JP2004068016A - Method for manufacturing foamed polypropylene resin particle, and formed polypropylene resin particle - Google Patents
Method for manufacturing foamed polypropylene resin particle, and formed polypropylene resin particle Download PDFInfo
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- JP2004068016A JP2004068016A JP2003277723A JP2003277723A JP2004068016A JP 2004068016 A JP2004068016 A JP 2004068016A JP 2003277723 A JP2003277723 A JP 2003277723A JP 2003277723 A JP2003277723 A JP 2003277723A JP 2004068016 A JP2004068016 A JP 2004068016A
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- 229910052719 titanium Inorganic materials 0.000 claims description 4
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- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 2
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- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
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- 230000000694 effects Effects 0.000 description 2
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- 238000000691 measurement method Methods 0.000 description 2
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- BIKXLKXABVUSMH-UHFFFAOYSA-N trizinc;diborate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]B([O-])[O-].[O-]B([O-])[O-] BIKXLKXABVUSMH-UHFFFAOYSA-N 0.000 description 2
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 1
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 1
- LVGUZGTVOIAKKC-UHFFFAOYSA-N 1,1,1,2-tetrafluoroethane Chemical compound FCC(F)(F)F LVGUZGTVOIAKKC-UHFFFAOYSA-N 0.000 description 1
- AHFMSNDOYCFEPH-UHFFFAOYSA-N 1,2-difluoroethane Chemical compound FCCF AHFMSNDOYCFEPH-UHFFFAOYSA-N 0.000 description 1
- PYSRRFNXTXNWCD-UHFFFAOYSA-N 3-(2-phenylethenyl)furan-2,5-dione Chemical compound O=C1OC(=O)C(C=CC=2C=CC=CC=2)=C1 PYSRRFNXTXNWCD-UHFFFAOYSA-N 0.000 description 1
- 229920002126 Acrylic acid copolymer Polymers 0.000 description 1
- XWCDCDSDNJVCLO-UHFFFAOYSA-N Chlorofluoromethane Chemical compound FCCl XWCDCDSDNJVCLO-UHFFFAOYSA-N 0.000 description 1
- PMPVIKIVABFJJI-UHFFFAOYSA-N Cyclobutane Chemical compound C1CCC1 PMPVIKIVABFJJI-UHFFFAOYSA-N 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
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- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 229920001400 block copolymer Polymers 0.000 description 1
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- 239000004566 building material Substances 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- NEHMKBQYUWJMIP-NJFSPNSNSA-N chloro(114C)methane Chemical compound [14CH3]Cl NEHMKBQYUWJMIP-NJFSPNSNSA-N 0.000 description 1
- HRYZWHHZPQKTII-UHFFFAOYSA-N chloroethane Chemical compound CCCl HRYZWHHZPQKTII-UHFFFAOYSA-N 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 239000002734 clay mineral Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
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- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 1
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- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
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- 235000019341 magnesium sulphate Nutrition 0.000 description 1
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- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
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- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
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- 230000003287 optical effect Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
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- 229920005675 propylene-butene random copolymer Polymers 0.000 description 1
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Abstract
Description
本発明は、ポリプロピレン系樹脂発泡粒子の製造方法及び該ポリプロピレン系樹脂発泡粒子に関する。 The present invention relates to a method for producing expanded polypropylene resin particles and the expanded polypropylene resin particles.
近年、ポリプロピレン系樹脂は、その機械強度、耐熱性、加工性、価格のバランスが優れていること及び易焼却性、易リサイクル性等の優れた性質を有することから利用分野を拡大しつつある。 In recent years, the field of application of polypropylene-based resins has been expanding due to their excellent balance of mechanical strength, heat resistance, workability, and price, and excellent properties such as easy incineration and easy recycling.
同様に、無架橋ポリプロピレン系樹脂からなる型内発泡成形体が、上記ポリプロピレン系樹脂の優れた性質を失うことなく、緩衝性、断熱性等の特性が付加されていることから、包装材料、建築材料、断熱材料等として広く利用されている。 Similarly, since the in-mold foam molded article made of a non-crosslinked polypropylene resin has properties such as cushioning and heat insulation added without losing the excellent properties of the above polypropylene resin, it can be used for packaging materials, building materials, etc. Widely used as materials, heat insulating materials, etc.
近年、特に自動車分野で軽量で高剛性の無架橋ポリプロピレン系樹脂からなる型内発泡成形体が要望され、高剛性のポリプロピレン系樹脂を用いて検討されている。高剛性のポリプロピレン系樹脂は、高剛性であるほど融点が高くなる傾向にある。高剛性のポリプロピレン系樹脂は、その融点が１４５℃以上のものが大半を占める。特に、ポリプロピレン系樹脂の融点が１４５℃以上となると型内成形に必要なスチーム圧力が高すぎるので、従来の成形機の耐圧性能（０．４５ＭＰａ(Ｇ)）を上回る結果、従来の成形機では発泡粒子同士の融着が不十分な成形体しか得ることができなかった。従って、従来のポリプロピレン系樹脂発泡粒子を型内成形するためには、高いスチーム圧力に耐える特別な成形装置が必要であった。更にポリプロピレン系樹脂の融点が１４５℃以上となる発泡粒子の場合は、成形時に使用するスチーム量が多大なものとなる問題が生じていた。 In recent years, there has been a demand for a lightweight and high-rigidity non-crosslinked polypropylene resin in-mold foam molded article particularly in the automobile field, and studies have been made using a high-rigidity polypropylene resin. The higher the rigidity, the higher the rigidity of the polypropylene resin tends to have a higher melting point. Most of the highly rigid polypropylene resin has a melting point of 145 ° C. or higher. In particular, when the melting point of the polypropylene-based resin is 145 ° C. or higher, the steam pressure required for in-mold molding is too high, and thus exceeds the pressure resistance performance (0.45 MPa (G)) of the conventional molding machine. Only a molded article with insufficient fusion between the expanded particles could be obtained. Therefore, a special molding apparatus that can withstand high steam pressure is required for in-mold molding of the conventional expanded polypropylene resin particles. Further, in the case of foamed particles in which the melting point of the polypropylene-based resin is 145 ° C. or higher, there has been a problem that the amount of steam used during molding becomes large.
かかる問題を解決し、従来の成形装置の耐圧以内であっても成形が可能な発泡成形体を得ることが試みられてきた。例えば、本出願人は、先に特許文献１に示すように、１４０℃以上の融点を有する第一のポリプロピレン系樹脂の粒状発泡体及びその表面に密着した第二のポリプロピレン系樹脂の発泡体よりなり、第二のポリプロピレン系樹脂の融点が第一のポリプロピレン系樹脂の融点より２〜１０℃低く、且つ特定の表面積を有するポリプロピレン系樹脂発泡粒子を提案した。しかし、該発泡粒子は、低圧のスチーム圧力で成型できるものの発泡粒子における芯層の剛性が低いため得られた発泡成形体の圧縮強度等の剛性は、低いものであった。
Attempts have been made to solve such a problem and obtain a foamed molded article that can be molded even within the pressure resistance of a conventional molding apparatus. For example, as shown in
また、特許文献２には、結晶性の熱可塑性樹脂からなる発泡状態の芯層と、該熱可塑性樹脂より融点が低いエチレン系重合体等から成り、且つ、実質的に非発泡状態である被覆層とから構成されている発泡粒子が提案されている。しかし、この発泡粒子を用いて得られた成形体は、加熱条件下での曲げ特性が低い等の耐熱性が低いという問題があった。 Patent Document 2 discloses a foamed core layer made of a crystalline thermoplastic resin and a coating made of an ethylene polymer or the like having a melting point lower than that of the thermoplastic resin and substantially non-foamed. Foamed particles composed of layers have been proposed. However, a molded article obtained by using the expanded particles has a problem in that heat resistance is low, such as low bending properties under heating conditions.
本発明は、従来のポリプロピレン系樹脂発泡粒子の加熱成型に必要とされるスチーム圧力よりも低いスチーム圧力にて加熱成型が可能であり、十分な剛性と、耐熱性を有する発泡成形体を得ることができるポリプロピレン系樹脂発泡粒子を提供することを目的とする。 The present invention is capable of performing heat molding at a steam pressure lower than the steam pressure required for heat molding of conventional polypropylene resin foam particles, to obtain a foam molded body having sufficient rigidity and heat resistance. It is an object of the present invention to provide expanded polypropylene resin particles that can be used.
本発明者等は、前記課題を解決すべく鋭意研究を重ねた結果、外層のポリプロピレン系樹脂が芯層のポリプロピレン系樹脂より融点が低く、外層の厚みを特定の値とした多層樹脂粒子に発泡剤を含浸させて、加熱軟化状態の発泡剤含浸多層樹脂粒子を発泡させて、実質的に非発泡の表層部とした発泡粒子は、表層部が発泡した発泡粒子とを比較した場合、実質的に非発泡の表層部とした発泡粒子は、成型する際、ポリプロピレン系樹脂の本来有する剛性等の特性を失うことなく低いスチーム圧力で発泡粒子相互を融着させることができることを見出し、本発明を完成させるに至った。 The present inventors have conducted intensive studies to solve the above problems, and as a result, the outer layer polypropylene resin has a lower melting point than the core layer polypropylene resin, and foams into multilayer resin particles having a specific outer layer thickness. The foaming agent-impregnated multilayer resin particles in the heat-softened state by foaming the foaming agent to form a substantially non-foamed surface layer. It has been found that foamed particles having a non-foamed surface layer portion can fuse foamed particles with each other at a low steam pressure without losing the inherent properties such as rigidity of a polypropylene resin during molding. It was completed.
即ち、本発明によれば、以下に示す発泡粒子の製造方法及び発泡粒子が提供される。 That is, according to the present invention, there are provided a method for producing foamed particles and a foamed particle described below.
［１］ポリプロピレン系樹脂から形成される芯層とポリプロピレン系樹脂から形成される外層とからなり、該外層のポリプロピレン系樹脂の融点（ｔｓ）と、該芯層のポリプロピレン系樹脂の融点（ｔｉ）との関係が（１）式を満足し、該外層の厚さが３０μｍ以下である多層樹脂粒子に発泡剤を含浸させることにより、加熱軟化状態の発泡剤含浸多層樹脂粒子を発泡させることを特徴とするポリプロピレン系樹脂発泡粒子の製造方法。
（数３）
１．５（℃）≦ｔｉ−ｔｓ≦３０．０（℃）・・・（１）
（但し、式中のｔｉ、ｔｓの単位はともに℃である。）
[1] Consisting of a core layer formed of a polypropylene resin and an outer layer formed of a polypropylene resin, the melting point (ts) of the polypropylene resin of the outer layer and the melting point (ti) of the polypropylene resin of the core layer Is satisfied by satisfying the expression (1), and by impregnating the foaming agent into the multilayer resin particles having an outer layer thickness of 30 μm or less, the foaming agent-impregnated multilayer resin particles in the heat-softened state are foamed. A method for producing expanded polypropylene resin particles.
(Equation 3)
1.5 (° C.) ≦ ti−ts ≦ 30.0 (° C.) (1)
(However, the units of ti and ts in the formula are both ° C.)
［２］芯層のポリプロピレン系樹脂の引張弾性率が１２００ＭＰａ以上であることを特徴とする前記［１］記載のポリプロピレン系樹脂発泡粒子の製造方法。 [2] The method for producing expanded polypropylene resin particles according to [1], wherein the tensile modulus of the polypropylene resin of the core layer is 1200 MPa or more.
［３］ポリプロピレン系樹脂から形成される芯層とポリプロピレン系樹脂から形成される外層とからなる多層樹脂粒子を発泡してなる発泡粒子であって、該発泡粒子は、該芯層のポリプロピレン系樹脂が発泡してなる内層部と該外層のポリプロピレン系樹脂からなる実質的に非発泡の表層部とからなり、マイクロ示差熱分析測定によって得られる該表層部の補外融解開始温度（Ｔｓ）が該内層部の補外融解開始温度（Ｔｉ）より少なくとも２℃低いことを特徴とするポリプロピレン系樹脂発泡粒子。 [3] Expanded particles obtained by expanding multilayer resin particles comprising a core layer formed of a polypropylene resin and an outer layer formed of a polypropylene resin, wherein the expanded particles are formed of a polypropylene resin of the core layer. Consists of an inner layer part formed by foaming and a substantially non-foamed surface layer part made of a polypropylene resin of the outer layer, and the extrapolative melting onset temperature (Ts) of the surface layer obtained by micro differential thermal analysis measurement is as follows. Foamed polypropylene resin particles, characterized by being at least 2 ° C. lower than the extrapolation melting start temperature (Ti) of the inner layer portion.
［４］表層部の補外融解開始温度（Ｔｓ）と、内層部の補外融解開始温度（Ｔｉ）との関係が（２）式を満足することを特徴とする前記［３］に記載のポリプロピレン系樹脂発泡粒子。
（数４）
３（℃）≦Ｔｉ−Ｔｓ≦４０（℃）・・・（２）
（但し、式中のＴｉ、Ｔｓの単位はともに℃である。）
[4] The above-mentioned [3], wherein the relationship between the extrapolation melting start temperature (Ts) of the surface layer portion and the extrapolation melting start temperature (Ti) of the inner layer portion satisfies the expression (2). Expanded polypropylene resin particles.
(Equation 4)
3 (° C.) ≦ Ti−Ts ≦ 40 (° C.) (2)
(However, the units of Ti and Ts in the formula are both ° C.)
［５］ポリプロピレン系樹脂発泡粒子の示差走査熱量測定によって得られるＤＳＣ曲線は、ポリプロピレン系樹脂に固有の吸熱曲線ピークと、該吸熱曲線ピークよりも高温側の吸熱曲線ピークとを少なくとも示し、且つ該高温側の吸熱曲線ピークの熱量が全ての吸熱曲線ピークの熱量の合計に対して１５％〜７０％であることを特徴とする前記［３］又は［４］に記載のポリプロピレン系樹脂発泡粒子。 [5] The DSC curve obtained by differential scanning calorimetry of the expanded polypropylene resin particles shows at least an endothermic curve peak unique to the polypropylene resin and an endothermic curve peak higher than the endothermic curve peak, and The expanded polypropylene resin particles according to [3] or [4], wherein the calorific value of the endothermic curve peak on the high temperature side is 15% to 70% with respect to the total caloric value of all endothermic curve peaks.
［６］ポリプロピレン系樹脂発泡粒子の形状が、筒状であることを特徴とする前記［３］〜［５］のいずれかに記載のポリプロピレン系樹脂発泡粒子。 [6] The expanded polypropylene resin particles according to any one of [3] to [5], wherein the expanded polypropylene resin particles have a cylindrical shape.
本発明方法により得られる発泡粒子は、多層樹脂粒子における外層の厚さを特定の値として、外層のポリプロピレン系樹脂の融点（ｔｓ）と、芯層のポリプロピレン系樹脂の融点（ｔｉ）との関係が特定の関系が成り立つようにすることで、発泡粒子における表層部を実質的に非発泡とするものである。これにより、得られる発泡粒子は、芯層のポリプロピレン系樹脂の融点が外層のポリプロピレン系樹脂の融点より高いものであっても低いスチーム圧力で発泡粒子相互の融着性に優れたものである。 In the foamed particles obtained by the method of the present invention, the relationship between the melting point (ts) of the polypropylene resin of the outer layer and the melting point (ti) of the polypropylene resin of the core layer, with the thickness of the outer layer in the multilayer resin particles being a specific value. Is to make the specific layer system hold, thereby making the surface layer portion of the foamed particles substantially non-foamed. As a result, even if the obtained foamed particles have a melting point of the polypropylene resin in the core layer higher than the melting point of the polypropylene resin in the outer layer, the foamed particles are excellent in fusion property between the foamed particles at a low steam pressure.
さらに、本発明方法により得られる発泡粒子は、芯層のポリプロピレン系樹脂の引張弾性率が特定の値であることから、バンパー等のエネルギー吸収材として使用する場合、優れたエネルギー吸収量を発泡成形体に付与することができる。 Furthermore, since the expanded particles obtained by the method of the present invention have a specific value in the tensile modulus of the polypropylene resin of the core layer, when used as an energy absorbing material such as a bumper, an excellent energy absorption amount is obtained by foam molding. Can be given to the body.
本発明の発泡粒子は、ポリプロピレン系樹脂から形成される芯層とポリプロピレン系樹脂から形成される外層とからなる多層樹脂粒子を発泡してなる発泡粒子であって、該発泡粒子は、該芯層のポリプロピレン系樹脂が発泡してなる内層部と該外層のポリプロピレン系樹脂からなる実質的に非発泡の表層部とからなり、マイクロ示差熱分析測定によって得られる該表層部の補外融解開始温度（Ｔｓ）が該内層部の補外融解開始温度（Ｔｉ）より少なくとも２℃低いことから芯層のポリプロピレン系樹脂の融点が外層のポリプロピレン系樹脂の融点より高いものであっても低いスチーム圧力にて加熱成形しても発泡粒子相互の融着性に優れた発泡粒子である。 The expanded particles of the present invention are expanded particles obtained by expanding multilayer resin particles including a core layer formed of a polypropylene resin and an outer layer formed of a polypropylene resin, and the expanded particles are formed of the core layer. Comprises an inner layer formed by foaming the polypropylene resin of the above and a substantially non-foamed surface layer formed of the polypropylene resin of the outer layer, and extrapolation melting start temperature of the surface layer obtained by micro differential thermal analysis measurement ( Since Ts) is at least 2 ° C. lower than the extrapolation melting start temperature (Ti) of the inner layer portion, even if the melting point of the polypropylene resin of the core layer is higher than the melting point of the polypropylene resin of the outer layer, it is possible to use a low steam pressure. The foamed particles are excellent in the fusion property between the foamed particles even when they are heat molded.
さらに、本発明の発泡粒子は、マイクロ示差熱分析測定によって得られる発泡粒子の表層部の補外融解開始温度（Ｔｓ）と、発泡粒子の内層部の補外融解開始温度（Ｔｉ）との関係が特定の式を満足する発泡粒子としたため、発泡成形体の耐熱性を低下させることなく、より低いスチーム圧力で成型できる発泡粒子である。 Further, in the expanded particles of the present invention, the relation between the extrapolation melting start temperature (Ts) of the surface layer portion of the expanded particles obtained by micro differential thermal analysis measurement and the extrapolation melting start temperature (Ti) of the inner layer portion of the expanded particles. Is a foamed particle which satisfies a specific formula, and thus can be molded at a lower steam pressure without lowering the heat resistance of the foamed molded article.
さらに、本発明の発泡粒子は、発泡粒子が発泡粒子の示差走査熱量測定によって得られるＤＳＣ曲線が、特定の構成であるという構成を採用すると、連続気泡率が低く、圧縮強度に優れ、容易に内圧を付与することができ、成形性が良好な発泡粒子を得ることができる。 Furthermore, the foamed particles of the present invention have a low open cell ratio, excellent compressive strength, and can be easily used when the DSC curve obtained by differential scanning calorimetry of the foamed particles is a specific configuration. An internal pressure can be applied, and foamed particles having good moldability can be obtained.
さらに、本発明の発泡粒子は、発泡粒子の形状が筒状であるという構成を採用すると、発泡成形体を成形する際に筒状の形状を崩さずに発泡粒子相互を融着させることができるので、空隙が高いポリプロピレン系樹脂発泡成形体が得られる。 Furthermore, when the foamed particles of the present invention employ a configuration in which the shape of the foamed particles is cylindrical, the foamed particles can be fused together without breaking the cylindrical shape when the foamed molded article is formed. Therefore, a polypropylene resin foam molded article having a high void can be obtained.
本発明のポリプロピレン系樹脂発泡粒子（以下、単に「発泡粒子」という）の製造方法は、ポリプロピレン系樹脂から形成される芯層とポリプロピレン系樹脂から形成される外層とからなる多層樹脂粒子に発泡剤を含浸させて、加熱軟化状態の発泡剤含浸多層樹脂粒子を発泡させる。 The method for producing expanded polypropylene resin particles (hereinafter, simply referred to as “expanded particles”) of the present invention comprises a method of adding a foaming agent to multilayer resin particles comprising a core layer formed of a polypropylene resin and an outer layer formed of the polypropylene resin. To expand the foamed agent-impregnated multilayer resin particles in a heat-softened state.
本発明の製造方法に用いられる多層樹脂粒子の芯層のポリプロピレン系樹脂としては、例えば、プロピレン単独重合体、またはプロピレン成分単位を６０モル％以上含有する（好ましくはプロピレン成分単位を８０モル％以上含有する）プロピレンと他のコモノマーとの共重合体のいずれか、あるいはこれらの樹脂の中から選ばれる２種以上の混合物が挙げられる。 Examples of the polypropylene resin of the core layer of the multilayer resin particles used in the production method of the present invention include a propylene homopolymer or a propylene component unit of 60 mol% or more (preferably, a propylene component unit of 80 mol% or more). (Containing) a copolymer of propylene and another comonomer, or a mixture of two or more selected from these resins.
プロピレン成分単位を６０モル％以上含有するプロピレンと他のコモノマーとの共重合体としては、例えば、プロピレン−エチレンランダムコポリマー、プロピレン−エチレンブロックコポリマー、プロピレン−ブテンランダムコポリマー、プロピレン−エチレン−ブテンランダムコポリマーなどが例示される。 Examples of copolymers of propylene containing at least 60 mol% of propylene component units with other comonomers include propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-butene random copolymer, and propylene-ethylene-butene random copolymer. And the like.
芯層のポリプロピレン系樹脂の融点は、最終的なポリプロピレン系樹脂型内発泡成形体（以下、「発泡成形体」という）の耐熱性を高いものとする上で、１４５℃以上であることが好ましく、１５５℃以上であることがより好ましく、１５８℃以上であることが更に好ましく、１６０℃以上であることが最も好ましい。該融点の上限値は、通常、１７０℃程度である。 The melting point of the polypropylene resin in the core layer is preferably 145 ° C. or higher in order to increase the heat resistance of the final foamed molded article in a polypropylene resin mold (hereinafter referred to as “foamed molded article”). 155 ° C. or higher, more preferably 158 ° C. or higher, and most preferably 160 ° C. or higher. The upper limit of the melting point is usually about 170 ° C.
また、芯層のポリプロピレン系樹脂は、発泡成形体の圧縮強度を大きいものとする上で、さらに発泡成形体をバンパー等のエネルギー吸収材として使用する場合のエネルギー吸収量が優れているという点で、引張降伏強さが３１ＭＰａ以上であることが好ましく、３２ＭＰａ以上であることがより好ましい。引張降伏強さの上限は特に規定はないが、通常は、大きくても４５ＭＰａである。 In addition, the polypropylene resin of the core layer, in order to increase the compressive strength of the foamed molded article, is superior in that the energy absorption amount when the foamed molded article is used as an energy absorbing material such as a bumper is excellent. The tensile yield strength is preferably at least 31 MPa, more preferably at least 32 MPa. Although the upper limit of the tensile yield strength is not particularly specified, it is usually at most 45 MPa.
また、芯層のポリプロピレン系樹脂は、多層樹脂粒子を発泡させる際に気泡膜が破れることを防止する上で、更には型内成形に際しての加熱時における気泡膜が破れることを防止する上で、引張破壊伸びが２０％以上であることが好ましく、１００％以上であることがより好ましく、２００〜１０００％であることが更に好ましい。 Further, the polypropylene resin of the core layer is to prevent the cell membrane from being broken when the multilayer resin particles are foamed, and further to prevent the cell membrane from being broken at the time of heating during in-mold molding. The tensile elongation at break is preferably 20% or more, more preferably 100% or more, and even more preferably 200 to 1000%.
尚、上記引張降伏強さ及び引張破壊伸びは、いずれも、ＪＩＳ Ｋ ６７５８（１９８１年）記載の測定方法に基づくものである。 Note that the tensile yield strength and tensile elongation at break are all based on the measurement method described in JIS K 6758 (1981).
特許文献１に記載されている表層部が発泡した発泡粒子は、芯層の剛性が低いことから得られた発泡成形体は、圧縮強度等の剛性が低いものである。より剛性が高いものとする上で本発明方法における芯層のポリプロピレン系樹脂は、引張弾性率が少なくとも１２００ＭＰａ以上であることが好ましい。かかる構成であると得られる発泡成形体がバンパー等のエネルギー吸収材として使用する場合、優れたエネルギー吸収量を付与する。このような観点から１２５０ＭＰａ以上であることがより好ましく、１３００ＭＰａ以上であることが更に好ましく、１３６０ＭＰａ〜２５００ＭＰａが特に好ましい。引張弾性率が１２００ＭＰａ以上の高剛性のポリプロピレン系樹脂としては、プロピレンの単独重合体の大半がそのような高剛性を示し、プロピレンと他のコモノマーとの共重合体であってもそのコモノマー成分含有割合が極端に少ないものはそのような高剛性を示す傾向にある。
発 泡 The foamed particles having a foamed surface layer described in
尚、引張弾性率は、樹脂をＪＩＳ Ｋ ７１６１（１９９４年）にしたがって以下の条件にて測定して求められた値である。
試験片：ＪＩＳ Ｋ ７１６２（１９９４年）記載の試験片１Ａ形（射出成形で直接成形）、
引張速度：１ｍｍ／分
The tensile modulus is a value obtained by measuring the resin under the following conditions according to JIS K7161 (1994).
Test piece: Specimen 1A type described in JIS K 7162 (1994) (direct molding by injection molding),
Tensile speed: 1 mm / min
また、芯層のポリプロピレン系樹脂は、ＭＦＲと略記されるメルトフローレート（ＪＩＳ Ｋ７２１０（１９７６年）の試験条件１４）が１ｇ／１０分以上１００ｇ／１０分以下であることが好ましい。該ＭＦＲが１ｇ／１０分未満であると、型内成形時の成形スチーム温度をより低くする効果が不充分となる虞がある。また、ＭＦＲが１００ｇ／１０分を越えると、得られた発泡成形体が脆くなる虞がある。このような観点から、ＭＦＲは１０ｇ／１０分以上７０ｇ／１０分以下であることがより好ましい。
前記特性を併せ持つポリプロピレン系樹脂は、種々の方法で製造された市販のポリプロピレン樹脂の中から入手可能である。
In addition, the polypropylene resin of the core layer preferably has a melt flow rate (test condition 14 of JIS K7210 (1976)) of 1 g / 10 min or more and 100 g / 10 min or less, abbreviated as MFR. If the MFR is less than 1 g / 10 minutes, the effect of lowering the molding steam temperature during in-mold molding may be insufficient. If the MFR exceeds 100 g / 10 minutes, the obtained foamed molded article may be brittle. From such a viewpoint, the MFR is more preferably from 10 g / 10 min to 70 g / 10 min.
Polypropylene resins having the above properties can be obtained from commercially available polypropylene resins produced by various methods.
芯層のポリプロピレン系樹脂には、本発明の所期の効果を損なわない範囲内において、ポリプロピレン系樹脂以外の他の合成樹脂、合成ゴム及び／又はエラストマー等を添加することができる。ポリプロピレン系樹脂以外の他の合成樹脂、合成ゴム及び／又はエラストマーの添加量は、ポリプロピレン系樹脂１００重量部当り、多くても３５重量部以下であることが好ましく、より好ましは２０重量部以下であり、更に好ましは１０重量部以下であり、多くても５重量部以下であることが最も好ましい。 合成 A synthetic resin, synthetic rubber, and / or an elastomer other than the polypropylene-based resin can be added to the polypropylene-based resin of the core layer as long as the intended effect of the present invention is not impaired. The amount of the synthetic resin, synthetic rubber and / or elastomer other than the polypropylene resin is preferably at most 35 parts by weight, more preferably at most 20 parts by weight, per 100 parts by weight of the polypropylene resin. And more preferably 10 parts by weight or less, and most preferably at most 5 parts by weight.
前記ポリプロピレン系樹脂以外の他の合成樹脂としては、高密度ポリエチレン、中密度ポリエチレン、低密度ポリエチレン、直鎖状低密度ポリエチレン、直鎖状超低密度ポリエチレン、エチレン−酢酸ビニル共重合体、エチレン−アクリル酸共重合体、エチレン−メタクリル酸共重合体等のエチレン系樹脂、或いはポリスチレン、スチレン−無水マレイン酸共重合体等のスチレン系樹脂等が例示される。 Other synthetic resins other than the polypropylene resin include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene- Examples thereof include an ethylene-based resin such as an acrylic acid copolymer and an ethylene-methacrylic acid copolymer, and a styrene-based resin such as polystyrene and a styrene-maleic anhydride copolymer.
前記合成ゴムとしては、エチレン−プロピレンゴム、エチレン−１−ブテンゴム、プロピレン−１−ブテンゴム、スチレン−ブタジエンゴムやその水添物、イソプレンゴム、ネオプレンゴム、ニトリルゴム等が例示される。前記エラストマーとしては、スチレン−ブタジエンブロック共重合体エラストマーやその水添物等が例示される。 Examples of the synthetic rubber include ethylene-propylene rubber, ethylene-1-butene rubber, propylene-1-butene rubber, styrene-butadiene rubber and hydrogenated products thereof, isoprene rubber, neoprene rubber, and nitrile rubber. Examples of the elastomer include a styrene-butadiene block copolymer elastomer and a hydrogenated product thereof.
なお、芯層のポリプロピレン系樹脂中には、所望に応じて各種添加剤を含有させることができる。このような添加剤としては、たとえば、酸化防止剤、紫外線防止剤、帯電防止剤、難燃剤、金属不活性剤、顔料、染料、核剤、あるいは気泡調整剤等を挙げることができる。気泡調整剤としては、たとえばホウ酸亜鉛、タルク、炭酸カルシウム、ホウ砂、水酸化アルミニウムなどの無機粉体が例示される。 ポ リ プ ロ ピ レ ン Various additives can be contained in the polypropylene resin of the core layer, if desired. Such additives include, for example, antioxidants, ultraviolet inhibitors, antistatic agents, flame retardants, metal deactivators, pigments, dyes, nucleating agents, and bubble regulators. Examples of the cell regulator include inorganic powders such as zinc borate, talc, calcium carbonate, borax, and aluminum hydroxide.
これらの添加剤の含有量は、芯層を形成するポリプロピレン系樹脂等からなる基材樹脂１００重量部当り２０重量部以下、特に５重量部以下であることが好ましい。特に、気泡調整剤の量は、平均気泡径を２０〜３００μｍとする上で０．００５〜１重量部であることが好ましい。 含有 The content of these additives is preferably 20 parts by weight or less, more preferably 5 parts by weight or less, per 100 parts by weight of the base resin composed of the polypropylene resin or the like forming the core layer. In particular, the amount of the cell regulator is preferably 0.005 to 1 part by weight in order to make the average cell diameter 20 to 300 μm.
本発明の製造方法に用いられる多層樹脂粒子の外層のポリプロピレン系樹脂としては、外層のポリプロピレン系樹脂の融点と芯層のポリプロピレン系樹脂の融点との関係が後述する（１）式を満足すること以外は、芯層のポリプロピレン系樹脂と同じものが例示される。 As for the polypropylene resin of the outer layer of the multilayer resin particles used in the production method of the present invention, the relationship between the melting point of the polypropylene resin of the outer layer and the melting point of the polypropylene resin of the core layer satisfies the following expression (1). Other than the above, the same as the polypropylene resin of the core layer are exemplified.
前記外層のポリプロピレン系樹脂の融点は、耐熱性の観点から１３０℃以上が好ましく、１４０℃以上がより好ましい。一方、その上限は、低い成形圧力で発泡粒子相互を融着させる観点から１５５℃以下が好ましく、１５０℃以下がより好ましく、１４５℃以下がさらに好ましい。 融 点 The melting point of the outer layer polypropylene-based resin is preferably 130 ° C or higher, more preferably 140 ° C or higher, from the viewpoint of heat resistance. On the other hand, the upper limit is preferably 155 ° C. or lower, more preferably 150 ° C. or lower, still more preferably 145 ° C. or lower, from the viewpoint of fusing the foamed particles with each other at a low molding pressure.
なお、外層のポリプロピレン系樹脂中には、前記芯層のポリプロピレン系樹脂と同様に、必要に応じて各種添加剤を含有させることができる。このような添加剤としては、たとえば、酸化防止剤、紫外線防止剤、帯電防止剤、難燃剤、金属不活性剤、顔料、染料、あるいは結晶核剤等を挙げることができる。中でも、酸化防止剤、紫外線防止剤、帯電防止剤、難燃剤、金属不活性剤、顔料、染料、あるいは結晶核剤等の機能性を付与する添加剤は、外層のみに添加するだけでその効果が得られる点で好ましい。 In addition, various additives can be contained in the polypropylene resin of the outer layer, if necessary, similarly to the polypropylene resin of the core layer. Examples of such additives include antioxidants, ultraviolet inhibitors, antistatic agents, flame retardants, metal deactivators, pigments, dyes, and crystal nucleating agents. Among them, additives that impart functionality such as antioxidants, ultraviolet inhibitors, antistatic agents, flame retardants, metal deactivators, pigments, dyes, or crystal nucleating agents are effective only by adding them to the outer layer only. Is preferred in that is obtained.
これらの添加剤の含有量は、外層のポリプロピレン系樹脂等からなる基材樹脂１００重量部当りおおよそ２０重量部以下、特に５重量部以下であることが好ましい。この下限は、概ね０．０１重量部である。 含有 The content of these additives is preferably about 20 parts by weight or less, particularly preferably 5 parts by weight or less, per 100 parts by weight of the base resin composed of the polypropylene resin or the like in the outer layer. The lower limit is approximately 0.01 parts by weight.
本発明方法においては、前記外層のポリプロピレン系樹脂の融点（ｔｓ）と、芯層のポリプロピレン系樹脂の融点（ｔｉ）との関係が下記（１）式を満足し、該外層の厚さが特定の値であるように構成される。かかる構成の多層樹脂粒子により、発泡された発泡粒子は、芯層のポリプロピレン系樹脂の融点が外層のポリプロピレン系樹脂の融点より高いものであっても低いスチーム圧力にて加熱成型しても発泡粒子相互の融着性に優れたものである。
さらに、発泡成形体の耐熱性を低下させることなく、より低いスチーム圧力で成型できる発泡粒子が得られる観点から下記（３）式を満足することが好ましく、下記（４）式を満足することがより好ましく、さらに下記（５）式を満足することがより好ましい。但し、式中の（ｔｉ）、（ｔｓ）の単位はともに℃である。
（数５）
１．５（℃）≦ｔｉ−ｔｓ≦３０．０（℃）・・・（１）
（数６）
１．５（℃）≦ｔｉ−ｔｓ≦２５．０（℃）・・・（３）
（数７）
１．５（℃）≦ｔｉ−ｔｓ≦２０．０（℃）・・・（４）
（数８）
１．５（℃）≦ｔｉ−ｔｓ≦１５．０（℃）・・・（５）
In the method of the present invention, the relationship between the melting point (ts) of the polypropylene resin of the outer layer and the melting point (ti) of the polypropylene resin of the core layer satisfies the following expression (1), and the thickness of the outer layer is specified. Is configured to be the value of The foamed particles foamed by the multilayer resin particles having the above-mentioned structure are foamed particles even if the melting point of the polypropylene resin in the core layer is higher than the melting point of the polypropylene resin in the outer layer, even when the resin is heated and molded at a low steam pressure. It is excellent in mutual fusion.
Further, from the viewpoint of obtaining foamed particles that can be molded at a lower steam pressure without lowering the heat resistance of the foam molded article, it is preferable that the following formula (3) is satisfied, and that the following formula (4) is satisfied. More preferably, it is more preferable to satisfy the following expression (5). However, the units of (ti) and (ts) in the formula are both ° C.
(Equation 5)
1.5 (° C.) ≦ ti−ts ≦ 30.0 (° C.) (1)
(Equation 6)
1.5 (° C.) ≦ ti−ts ≦ 25.0 (° C.) (3)
(Equation 7)
1.5 (° C.) ≦ ti−ts ≦ 20.0 (° C.) (4)
(Equation 8)
1.5 (° C.) ≦ ti−ts ≦ 15.0 (° C.) (5)
前記外層のポリプロピレン系樹脂の融点（ｔｓ）は、ＪＩＳ Ｋ７１２２（１９８７年）に準拠する測定方法により得られた値を採用する。
多層樹脂粒子を作製する際、外層用の原料として用いられるポリプロピレン系樹脂２〜４ｍｇを採取し、示差走査熱量計によって室温（１０〜４０℃）から２２０℃まで１０℃／分で昇温測定を行なう。その後、４０℃まで１０℃／分の速度で下げ、４０℃となってから再び、２２０℃まで１０℃／分で昇温測定を行なう。かかる測定により得られた２回目の昇温により得られるＤＳＣ曲線のピークの頂点を融点とする。なお、ピークが２つ以上ある場合、熱量が最も大きい融解ピークの頂点を採用する。
As the melting point (ts) of the polypropylene resin of the outer layer, a value obtained by a measuring method based on JIS K7122 (1987) is employed.
When preparing the multilayer resin particles, 2 to 4 mg of a polypropylene resin used as a raw material for the outer layer is sampled, and the temperature is measured by a differential scanning calorimeter from room temperature (10 to 40 ° C.) to 220 ° C. at a rate of 10 ° C./min. Do. Thereafter, the temperature is lowered at a rate of 10 ° C./min to 40 ° C., and after the temperature reaches 40 ° C., the temperature is again measured at a rate of 10 ° C./min to 220 ° C. The peak of the peak of the DSC curve obtained by the second temperature increase obtained by such measurement is defined as the melting point. When there are two or more peaks, the peak of the melting peak having the largest calorific value is adopted.
また、芯層のポリプロピレン系樹脂の融点（ｔｉ）は、前記した外層のポリプロピレン系樹脂の融点（ｔｓ）の測定方法と同様にして得られた値を採用する。 (4) As the melting point (ti) of the polypropylene resin of the core layer, a value obtained in the same manner as the above-described method of measuring the melting point (ts) of the polypropylene resin of the outer layer is employed.
本発明方法においては、多層樹脂粒子における芯層のポリプロピレン系樹脂の融点（ｔｉ）と前記した外層のポリプロピレン系樹脂の融点（ｔｓ）との関係が特定の式を満足し、前記外層の厚さが３０μｍ以下となるように多層樹脂粒子を形成する。かかる構成により、多層樹脂粒子を発泡させた際に芯層は発泡するが外層は発泡しないので、外層が発泡した発泡粒子よりも低いスチーム圧力で成型できる発泡粒子が得られる。
前記した多層樹脂粒子の外層が発泡しないメカニズムについては、定かではないが多層樹脂粒子が発泡する際、発泡力と樹脂の溶融粘度との関係で発泡剤を保持するためにはある程度の樹脂の厚さが必要であると考えられ、多層樹脂粒子の外層の厚さを特定の値し、芯層のポリプロピレン系樹脂の融点（ｔｉ）と前記した外層のポリプロピレン系樹脂の融点（ｔｓ）との関係が特定の式を満足することで多層樹脂粒子の芯層を発泡させ、外層を実質的に非発泡とすることができると考えられる。
In the method of the present invention, the relationship between the melting point (ti) of the polypropylene resin of the core layer in the multilayer resin particles and the melting point (ts) of the polypropylene resin of the outer layer satisfies a specific formula, and the thickness of the outer layer is Is formed to be 30 μm or less. With such a configuration, when the multilayer resin particles are foamed, the core layer foams but the outer layer does not foam, so that foamed particles that can be molded with a lower steam pressure than the foamed foam of which the outer layer has foamed are obtained.
The mechanism by which the outer layer of the multilayer resin particles does not foam is not clear, but when the multilayer resin particles foam, a certain amount of resin thickness is required to hold the blowing agent in relation to the foaming power and the melt viscosity of the resin. It is considered necessary to determine the thickness of the outer layer of the multilayer resin particles, and determine the relationship between the melting point (ti) of the polypropylene resin of the core layer and the melting point (ts) of the polypropylene resin of the outer layer. It is considered that when the formula satisfies a specific formula, the core layer of the multilayer resin particles can be foamed and the outer layer can be substantially non-foamed.
本発明方法において、多層樹脂粒子の外層の厚さの下限値は、発泡粒子相互の融着性が優れているという観点から１μｍ以上が好ましく、２μｍ以上がより好ましく、３μｍ以上が特に好ましい。一方、上限値は、発泡させない観点から２５μｍ以下が好ましく、１８μｍ以下がより好ましく、１５μｍ以下が特に好ましい。 に お い て In the method of the present invention, the lower limit of the thickness of the outer layer of the multilayer resin particles is preferably 1 μm or more, more preferably 2 μm or more, and particularly preferably 3 μm or more from the viewpoint of excellent fusion property between the expanded particles. On the other hand, the upper limit is preferably 25 μm or less, more preferably 18 μm or less, and particularly preferably 15 μm or less, from the viewpoint of preventing foaming.
本明細書の多層樹脂粒子における外層の厚みは、多層樹脂粒子を、二等分して断面を顕微鏡下にて断面が全て入るようになるべく大きく拡大し、さらに該多層樹脂粒子を二等分した垂直な断面において外層が全周に写るように光学顕微鏡にて撮影した写真から測定される。具体的には、写真上で断面がおおよそ二等分となるように直線を引き、さらにその直線に直角となるように直線を引き、それらの直線と外層部分とが接する４箇所の長さを求め、その平均を一つの多層樹脂粒子の外層の厚みとする。この作業を合わせて１０個の発泡粒子について行い、相加平均した値を多層樹脂粒子における外層の厚みとする。多層樹脂粒子における外層の厚みが分かりづらいときは予め外層を構成する樹脂に着色剤を添加して多層樹脂粒子を製造することが好ましい。 The thickness of the outer layer in the multilayer resin particles of the present specification, the multilayer resin particles, bisecting the cross section, enlarged as much as possible so that the cross-section is all under the microscope, further bisecting the multilayer resin particles It is measured from a photograph taken with an optical microscope so that the outer layer appears on the entire circumference in a vertical cross section. Specifically, a straight line is drawn so that the cross section is approximately bisected on the photograph, and a straight line is drawn so as to be perpendicular to the straight line. The average is determined as the thickness of the outer layer of one multilayer resin particle. This operation is performed for 10 foamed particles in total, and the arithmetically averaged value is defined as the thickness of the outer layer of the multilayer resin particles. When the thickness of the outer layer in the multilayer resin particles is difficult to understand, it is preferable to add a coloring agent to the resin constituting the outer layer in advance to produce the multilayer resin particles.
本発明方法において得られる発泡粒子は、通常の発泡粒子（多層構造でない発泡粒子）と比較して成型する際、発泡粒子の二次発泡性が劣り、得られる発泡成形体は金型と同じ形状となる金型転写性が低いことから平均気泡径が２０μｍ以上とすることが好ましい。前述した観点から２５μｍ以上がより好ましく、３０μｍ以上がさらに好ましい。一方、その上限値は、得られる発泡成形体が圧縮応力により気泡が破泡することがなく、そのため歪が残らず繰り返し使用することができる観点から３００μｍ以下が好ましい。上記観点から２５０μｍ以下がより好ましく、２００μｍがさらに好ましい。
なお、平均気泡径の測定方法は、発泡粒子を、二等分して断面を顕微鏡下にて断面が全て入るようになるべく大きく拡大してその断面を撮影する。その写真に基づき写真上で断面がおおよそ二等分となるように直線を引き、直線の長さを直線に接するすべての気泡の数で除した値をひとつの発泡粒子の平均気泡径とし、同様にして２０個の発泡粒子について求め、その相加平均を発泡粒子の平均気泡径として採用した。
The foamed particles obtained by the method of the present invention are inferior in the secondary expandability of the foamed particles when molded as compared with ordinary foamed particles (foamed particles having no multilayer structure), and the obtained foamed molded product has the same shape as the mold. It is preferable that the average bubble diameter be 20 μm or more because of low mold transferability. From the viewpoints described above, the thickness is more preferably 25 μm or more, and still more preferably 30 μm or more. On the other hand, the upper limit is preferably 300 μm or less from the viewpoint that the foamed article obtained does not break bubbles due to compressive stress, and thus can be used repeatedly without remaining distortion. From the above viewpoint, the thickness is more preferably equal to or less than 250 μm, and further preferably 200 μm.
In the meantime, the method for measuring the average cell diameter is to divide the foamed particles into two equal parts, and to enlarge the cross section under a microscope as much as possible so that the entire cross section can be included, and photograph the cross section. Based on the photograph, draw a straight line so that the cross-section is roughly bisected on the photograph, and divide the length of the straight line by the number of all bubbles in contact with the straight line as the average cell diameter of one expanded particle, and And the arithmetic mean thereof was adopted as the average cell diameter of the foamed particles.
本発明方法において用いる多層樹脂粒子の形状としては、例えば、円柱状、ラクビーボール状、球状、筒状が挙げられる。かかる多層樹脂粒子を発泡して得られる発泡粒子は、発泡前の形状に応じて円柱状、球状、ラクビーボール状、筒状となる。これらの形状の中では、筒状を選択すると空隙率の高い発泡成形体を得ることができ、かかる発泡成形体は透水性に優れたものである。 多層 Examples of the shape of the multilayer resin particles used in the method of the present invention include a columnar shape, a rugby ball shape, a spherical shape, and a cylindrical shape. The foamed particles obtained by foaming such multilayer resin particles have a columnar shape, a spherical shape, a rugby ball shape, or a cylindrical shape according to the shape before foaming. Among these shapes, when a tubular shape is selected, a foam molded article having a high porosity can be obtained, and such a foam molded article has excellent water permeability.
本発明において前記したポリプロピレン系樹脂発泡粒子の形状が筒状であるとは、円柱、楕円柱、角柱等の柱状発泡粒子の柱の上下方向を貫通する１又は２以上の貫通孔を有する形状のもの（例えば、特開平７−１３７０６３号の図２の（ア）乃至（カ））のみならず、上記貫通孔を有する形状に加え、外表面の一部に羽根状の突起を有する中空状のもの（例えば、特開平７−１３７０６３号の図３の（チ）乃至（ナ））や、上記貫通孔を有する形状に加え、一部に断裂部を有する中空円形状のもの（例えば、特開平７−１３７０６３号の図２の（キ））や上記貫通孔を有する形状に加え、一部に断裂部を有する中空多角形状のもの（例えば、特開平７−１３７０６３号の図２の（ク））をも包含する。 In the present invention, the polypropylene resin expanded particles having a cylindrical shape means that the column has one or two or more through-holes penetrating vertically through the columns of the columnar expanded particles such as a column, an elliptic column, and a prism. In addition to the shape having the through-holes described above (for example, FIGS. 2A to 2K of JP-A-7-137063), a hollow shape having wing-shaped protrusions on a part of the outer surface is also provided. (For example, Japanese Patent Application Laid-Open No. 7-137063, FIG. 3 (h) to FIG. 3 (n)), and in addition to the above-mentioned shape having a through hole, a hollow circular shape having a tear part in a part (for example, In addition to the shape having a through-hole and a hollow polygonal shape having a partly broken portion in addition to the shape having a through hole (for example, FIG. 2 (g) of JP-A-7-137063), FIG. ).
次に、本発明の多層樹脂粒子を製造する方法の一例について説明する。 Next, an example of a method for producing the multilayer resin particles of the present invention will be described.
まず、芯層を構成する前記ポリプロピレン系樹脂と必要に応じて配合される他の樹脂と添加剤とをひとつの押出機に供給し、加熱し混練して芯層形成用の第一の混合溶融樹脂を形成する。同時に、外層を構成する前記ポリプロピレン系樹脂と必要に応じて配合される他の樹脂と添加剤とを他の押出機に供給し、加熱し混練して外層形成用の第二の混合溶融樹脂を形成する。 First, the polypropylene-based resin constituting the core layer, the other resin and the additives, which are blended as required, are supplied to one extruder, heated and kneaded to form a first mixed melt for forming the core layer. Form a resin. At the same time, the polypropylene-based resin constituting the outer layer and the other resin and additives to be blended as needed are supplied to another extruder, heated and kneaded to form a second mixed molten resin for forming the outer layer. Form.
次に、第一の混合溶融樹脂と第二の混合溶融樹脂とを共押出ダイに供給し、該ダイ内において、第二の混合溶融樹脂の流れが第一の混合溶融樹脂のストランド状の流れの周囲を覆うように、第一の混合溶融樹脂の流れと第二の混合溶融樹脂の流れとを合流させ、両者を積層する。次に、積層された混合溶融樹脂を、ダイからストランド状に押出して冷却してから切断することにより、多層樹脂粒子を製造することができる。 Next, the first mixed molten resin and the second mixed molten resin are supplied to a co-extrusion die. In the die, the flow of the second mixed molten resin is a strand-like flow of the first mixed molten resin. The flow of the first mixed molten resin and the flow of the second mixed molten resin are merged so as to cover the periphery of the first resin, and the two are laminated. Next, the laminated mixed molten resin is extruded into a strand shape from a die, cooled, and then cut, whereby multilayer resin particles can be manufactured.
なお、多層樹脂粒子における外層の厚さの調整は、芯層の吐出量と外層の吐出量とのバランスの調整や、ストランド状の押出物を引き取る速度を調整することにより行なう。 The thickness of the outer layer of the multilayer resin particles is adjusted by adjusting the balance between the discharge amount of the core layer and the discharge amount of the outer layer, and by adjusting the speed at which the strand-shaped extrudate is drawn.
このように、ストランド状に共押出してから切断することが、外層が芯層に積層された多層樹脂粒子を得ることができるので好ましい。但し、本発明においては、芯層を形成する樹脂に外層を形成する樹脂が積層された多層シートを押出し、該シートを裁断して粒状にする方法を採用してもよい。 共 Such a co-extrusion in the form of a strand and then cutting are preferable because multilayer resin particles having an outer layer laminated on a core layer can be obtained. However, in the present invention, a method of extruding a multilayer sheet in which a resin forming an outer layer is laminated on a resin forming a core layer and cutting the sheet into granules may be employed.
多層樹脂粒子の表面積における外層の占める面積は、多層樹脂粒子を発泡させて得られた発泡粒子に優れた融着性を付与し、さらには曲げ強度に優れた発泡成形体を得ることができる点で表面積の全体の５０％以上を占めることが好ましく、６０％以上がより好ましく、７０％以上が特に好ましい。なお、多層樹脂粒子の表面積における外層が線状に被覆されていても構わない。 The area occupied by the outer layer in the surface area of the multilayer resin particles is such that foamed particles obtained by foaming the multilayer resin particles are provided with excellent fusion bonding properties, and furthermore, a foam molded article having excellent bending strength can be obtained. Occupies 50% or more of the entire surface area, more preferably 60% or more, and particularly preferably 70% or more. In addition, the outer layer in the surface area of the multilayer resin particles may be linearly coated.
次に、前記多層樹脂粒子を用いて、発泡粒子を発泡する方法の好ましい一例を説明する。 Next, a preferred example of a method for foaming foamed particles using the multilayer resin particles will be described.
まず、前記多層樹脂粒子を発泡剤等と共にオートクレーブ等の密閉容器内において水やアルコール等の水性媒体に分散させ、芯層を形成するポリプロピレン系樹脂の軟化温度以上の温度に加熱し、多層樹脂粒子に発泡剤を含浸させる。次に、密閉容器内の圧力を発泡剤の蒸気圧以上の圧力に保持しながら、密閉容器内の水面下の一端を開放し、多層樹脂粒子と水性媒体とを同時に容器内よりも低圧の雰囲気下に放出する（以下、分散媒放出発泡方法という）。通常、取り扱い上の観点から前記した水性媒体は水が好ましい。 First, the multilayer resin particles are dispersed in an aqueous medium such as water or alcohol in an airtight container such as an autoclave together with a foaming agent and the like, and heated to a temperature equal to or higher than the softening temperature of the polypropylene resin forming the core layer. Is impregnated with a blowing agent. Next, while maintaining the pressure in the closed container at a pressure equal to or higher than the vapor pressure of the blowing agent, one end below the water surface in the closed container is opened, and the multilayer resin particles and the aqueous medium are simultaneously exposed to an atmosphere at a lower pressure than in the container. It is discharged below (hereinafter referred to as a dispersion medium release foaming method). Usually, water is preferable as the aqueous medium from the viewpoint of handling.
分散媒放出発泡方法においては、容器内で加熱された場合に多層樹脂粒子同士が容器内で互いに融着しないように、分散媒体中に分散剤を添加することが好ましい。そのような分散剤としては、多層樹脂粒子の容器内での融着を防止するものであればよく、有機系、無機系を問わず使用可能であるが、取り扱いのし易さから微粒状無機物が好ましい。例えば、アムスナイト、カオリン、マイカ、クレー等の天然又は合成粘土鉱物や、酸化アルミニウム、酸化チタン、塩基性炭酸マグネシウム、塩基性炭酸亜鉛、炭酸カルシウム、酸化鉄等を１種または数種の組み合わせで使用してもよい。尚、分散剤は、通常多層樹脂粒子１００重量部当り、０．００１〜５重量部程度使用される。 In the dispersion medium release foaming method, it is preferable to add a dispersant to the dispersion medium so that the multilayer resin particles do not fuse together in the container when heated in the container. As such a dispersing agent, any dispersing agent can be used as long as it prevents fusion of the multilayer resin particles in the container, and it can be used regardless of whether it is organic or inorganic. Is preferred. For example, natural or synthetic clay minerals such as amsunite, kaolin, mica, clay, and the like, aluminum oxide, titanium oxide, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, iron oxide, etc., in one kind or in combination of several kinds May be used. The dispersant is usually used in an amount of about 0.001 to 5 parts by weight per 100 parts by weight of the multilayer resin particles.
更に、分散媒放出発泡方法においては、分散剤の分散力を強化する分散強化剤（分散剤の添加量が少ない場合であっても、容器内における多層樹脂粒子同士の融着を防止する機能を有する。）を分散媒体中に添加してもよい。このような分散強化剤としては、４０℃の水１００ｃｃに対して少なくとも１ｍｇ以上溶解し得る無機化合物であって、該化合物の陰イオンまたは陽イオンの少なくとも一方が２価または３価の無機物質が好ましい。このような無機物質としては、たとえば、塩化マグネシウム、硝酸マグネシウム、硫酸マグネシウム、塩化アルミニウム、硝酸アルミニウム、硫酸アルミニウム、塩化鉄、硫酸鉄、硝酸鉄等が例示される。見かけ密度が１００ｇ／Ｌ以上の低発泡の発泡粒子を製造する場合には、分散強化剤を使用することが好ましい。
尚、分散強化剤は、通常多層樹脂粒子１００重量部当り０．０００１〜１重量部程度使用される。
Further, in the dispersion medium release foaming method, a dispersion strengthening agent for enhancing the dispersing power of the dispersant (a function for preventing fusion of the multilayer resin particles in the container even when the amount of the dispersant added is small). May be added to the dispersion medium. Such a dispersion enhancer is an inorganic compound that can be dissolved in at least 1 mg or more in 100 cc of water at 40 ° C., and at least one of the anion and the cation of the compound is a divalent or trivalent inorganic substance. preferable. Examples of such an inorganic substance include magnesium chloride, magnesium nitrate, magnesium sulfate, aluminum chloride, aluminum nitrate, aluminum sulfate, iron chloride, iron sulfate, and iron nitrate. When producing foamed particles of low foaming having an apparent density of 100 g / L or more, it is preferable to use a dispersion enhancer.
The dispersion enhancer is usually used in an amount of about 0.0001 to 1 part by weight per 100 parts by weight of the multilayer resin particles.
分散媒放出発泡方法において用いる発泡剤としては、例えば、プロパン、ブタン、ヘキサン、ヘプタン等の脂肪族炭化水素類、シクロブタン、シクロヘキサン等の環式脂肪族炭化水素類、クロロフロロメタン、トリフロロメタン、１，２−ジフロロエタン、１，２，２，２−テトラフロロエタン、メチルクロライド、エチルクロライド、メチレンクロライド等のハロゲン化炭化水素などの有機系物理発泡剤や、窒素、酸素、空気、二酸化炭素、水といったいわゆる無機系物理発泡剤が例示される。また有機系物理発泡剤と無機系物理発泡剤を併用することもできる。前記した物理発泡剤は低密度の発泡粒子が容易に得られる点から好ましい。
上記物理発泡剤の中でも、窒素、酸素、空気、二酸化炭素、水の群から選択される１又は２以上の無機系物理発泡剤を主成分とするものが好適である。更に、これらの中でも発泡粒子の見かけ密度の安定性、環境負荷やコストなどを考慮すると、窒素や空気が好ましい。また発泡剤として水を使用する場合は、多層樹脂粒子を密閉容器中に分散させるための分散媒体として使用する水をそのまま利用すればよい。
As the foaming agent used in the dispersion medium release foaming method, for example, aliphatic hydrocarbons such as propane, butane, hexane, heptane, cycloaliphatic hydrocarbons such as cyclobutane and cyclohexane, chlorofluoromethane, trifluoromethane, Organic physical blowing agents such as halogenated hydrocarbons such as 1,2-difluoroethane, 1,2,2,2-tetrafluoroethane, methyl chloride, ethyl chloride, and methylene chloride; nitrogen, oxygen, air, carbon dioxide, So-called inorganic physical foaming agents such as water are exemplified. Further, an organic physical foaming agent and an inorganic physical foaming agent can be used in combination. The above-mentioned physical foaming agent is preferable because low-density foamed particles can be easily obtained.
Among the above physical foaming agents, those mainly containing one or more inorganic physical foaming agents selected from the group consisting of nitrogen, oxygen, air, carbon dioxide and water are preferred. Further, among these, nitrogen and air are preferable in consideration of the stability of the apparent density of the expanded particles, the environmental load, the cost, and the like. When water is used as the foaming agent, water used as a dispersion medium for dispersing the multilayer resin particles in the closed container may be used as it is.
分散媒放出発泡方法における物理発泡剤の容器内への充填量は、使用する発泡剤の種類と発泡温度と目的とする発泡粒子の見かけ密度に応じて適宜選択される。具体的には、例えば発泡剤として窒素を使用し、分散媒体として水を使用した場合、発泡開始直前の安定した状態にある密閉容器内の圧力、すなわち密閉容器内空間部の圧力（ゲージ圧）が、０．６〜６ＭＰａとなるように選定することが好ましい。尚、一般的に、目的とする発泡粒子の見かけ密度が小さいほど前記容器内の空間部の圧力は高くすることが望ましく、目的とする発泡粒子の見かけ密度が大きいほど空間部の圧力は低くすることが望ましい。 (4) The amount of the physical foaming agent charged into the container in the dispersion medium release foaming method is appropriately selected according to the type of the foaming agent to be used, the foaming temperature, and the apparent density of the intended foamed particles. Specifically, for example, when nitrogen is used as a foaming agent and water is used as a dispersion medium, the pressure in the closed container in a stable state immediately before the start of foaming, that is, the pressure (gauge pressure) in the space inside the closed container. Is preferably selected to be 0.6 to 6 MPa. In general, it is desirable that the smaller the apparent density of the target expanded particles, the higher the pressure in the space in the container, and the higher the apparent density of the target expanded particles, the lower the pressure in the space. It is desirable.
分散媒放出発泡方法における物理発泡剤の容器内への充填は、昇温と同時に充填しても、昇温の途中に充填しても、発泡開始直前の安定した状態に充填しても多層樹脂粒子に発泡剤が含浸していれば構わない。 In the dispersion medium release foaming method, the physical foaming agent can be filled into the container at the same time as the temperature rise, during the temperature rise, or in a stable state immediately before the start of foaming. It does not matter if the particles are impregnated with a foaming agent.
本発明方法において発泡剤を含浸させた多層樹脂粒子を加熱軟化し発泡させる方法としては、以上説明した分散媒放出発泡方法に限定されるものでなく、前記した発泡剤を用いて、特開平４−３７２６３０号に記載されているように発泡剤を含浸させた発泡性多層樹脂粒子を加熱蒸気や、熱風等の加熱媒体により発泡させる方法でもよい。 The method of heating and softening the multilayer resin particles impregnated with the foaming agent in the method of the present invention to foam them is not limited to the dispersion medium release foaming method described above. As described in JP-A-372630, a method may be used in which foamable multilayer resin particles impregnated with a foaming agent are foamed with a heating medium such as heated steam or hot air.
本発明の発泡粒子は、前述した方法により好ましく製造され、ポリプロピレン系樹脂から形成される芯層とポリプロピレン系樹脂から形成される外層とからなる多層樹脂粒子を発泡してなる発泡粒子であって、該発泡粒子は、該芯層のポリプロピレン系樹脂が発泡してなる内層部と該外層のポリプロピレン系樹脂からなる実質的に非発泡の表層部とからなり、マイクロ示差熱分析測定によって得られる該表層部の補外融解開始温度が該内層部の補外融解開始温度より少なくとも２℃低いものである。
このように構成されていると、芯層のポリプロピレン系樹脂の融点が外層のポリプロピレン系樹脂の融点より高いものであっても低いスチーム圧力にて加熱成形しても発泡粒子相互の融着性に優れた発泡粒子である。
The expanded particles of the present invention are preferably manufactured by the above-described method, and are expanded particles obtained by expanding multilayer resin particles including a core layer formed of a polypropylene resin and an outer layer formed of the polypropylene resin, The foamed particles are composed of an inner layer portion formed by foaming the polypropylene resin of the core layer and a substantially non-foamed surface layer portion formed of the outer layer polypropylene resin, and the surface layer obtained by micro differential thermal analysis measurement. The extrapolation melting start temperature of the part is at least 2 ° C. lower than the extrapolation melting start temperature of the inner layer part.
With such a configuration, even if the melting point of the polypropylene resin of the core layer is higher than the melting point of the polypropylene resin of the outer layer, even if it is heat-molded at a low steam pressure, the fusion property between the foamed particles can be improved. Excellent foam particles.
なお、本明細書において外層のポリプロピレン系樹脂からなる実質的に非発泡の表層部であるとは、１００個の発泡粒子における表層部の断面写真（拡大倍率２００倍）を１００枚撮影して、その内、表層部が発泡している断面写真は１０枚以下が好ましく、５枚以下がより好ましい。 In the present specification, a substantially non-foamed surface layer portion made of a polypropylene-based resin of the outer layer means that 100 cross-sectional photographs (magnification: 200 times) of the surface layer portion of 100 foamed particles are taken. Among them, the number of cross-sectional photographs in which the surface layer is foamed is preferably 10 or less, more preferably 5 or less.
本発明の発泡粒子の外層を形成するポリプロピレン系樹脂は、前述した本発明方法で用いる発泡粒子の外層を形成するポリプロピレン系樹脂と同様なポリプロピレン系樹脂が挙げられる。本発明の発泡粒子の芯層を形成するポリプロピレン系樹脂は、前述した本発明方法で用いる発泡粒子の芯層を形成するポリプロピレン系樹脂と同様なポリプロピレン系樹脂が挙げられる。 ポ リ プ ロ ピ レ ン The polypropylene resin forming the outer layer of the foamed particles of the present invention includes the same polypropylene resin as the polypropylene resin forming the outer layer of the foamed particles used in the method of the present invention described above. Examples of the polypropylene resin forming the core layer of the foamed particles of the present invention include the same polypropylene resin as the polypropylene resin forming the core layer of the foamed particles used in the method of the present invention described above.
本発明の発泡粒子は、内層部のポリプロピレン系樹脂と該表層部のポリプロピレン系樹脂と異なる樹脂が好ましい。本明細書でいう異なる樹脂とは、融点、融解開始温度、ＭＦＲ及びビカット軟化温度のいずれかひとつが異なることをいう。前記した融点、補外融解開始温度及びビカット軟化温度の値は、表層部の値が内層部の値よりも小さいものである。また、ＭＦＲの値は、表層部の値が内層部の値よりも大きいものである。上記物性値は、発泡粒子の表層部をカッターなどで切り取った樹脂を用いることとし、発泡粒子の内層部は、表層部が入らないように切り取り、脱泡させた樹脂を用いることとする。 発 泡 The expanded particles of the present invention are preferably different from the polypropylene resin in the inner layer and the polypropylene resin in the surface layer. The term “different resin” as used herein means that any one of the melting point, melting start temperature, MFR and Vicat softening temperature is different. The values of the melting point, extrapolation melting start temperature and Vicat softening temperature are such that the value of the surface layer is smaller than the value of the inner layer. The value of the MFR is such that the value of the surface layer is larger than the value of the inner layer. For the above physical property values, a resin obtained by cutting the surface layer of the foamed particles with a cutter or the like is used, and for the inner layer of the foamed particles, a resin that is cut off and defoamed so that the surface layer does not enter is used.
本発明の発泡粒子においてはマイクロ示差熱分析測定を行った場合、表層部の補外融解開始温度（Ｔｓ）と、内層部の補外融解開始温度（Ｔｉ）との関係が下式を満足する発泡粒子であることが発泡成形体の耐熱性を低下させることなく、より低いスチーム圧力で成型できる発泡粒子となる観点から好ましい。但し、式中のＴｉ、Ｔｓの単位はともに℃である。
（数９）
３（℃）≦Ｔｉ−Ｔｓ≦４０（℃）・・・（２）
In the expanded particles of the present invention, when the micro-differential thermal analysis measurement is performed, the relation between the extrapolation melting start temperature (Ts) of the surface layer portion and the extrapolation melting start temperature (Ti) of the inner layer portion satisfies the following expression. The expanded particles are preferred from the viewpoint that the expanded particles can be molded at a lower steam pressure without lowering the heat resistance of the expanded molded article. However, the units of Ti and Ts in the formula are both ° C.
(Equation 9)
3 (° C.) ≦ Ti−Ts ≦ 40 (° C.) (2)
低いスチーム圧でも加熱成型することができると共に、得られる発泡成形体の耐熱性の低下を防ぐという観点からは、下記（６）式を満足することが好ましく、下記（７）式を満足することがより好ましく、下記（８）式を満足することがさらに好ましく、下記（９）式を満足することが特に好ましくい。但し、式中のＴｉ、Ｔｓの単位はともに℃である。
（数１０）
３（℃）≦Ｔｉ−Ｔｓ≦４０（℃）・・・（６）
（数１１）
５（℃）≦Ｔｉ−Ｔｓ≦４０（℃）・・・（７）
（数１２）
７（℃）≦Ｔｉ−Ｔｓ≦４０（℃）・・・（８）
（数１３）
９（℃）≦Ｔｉ−Ｔｓ≦４０（℃）・・・（９）
From the viewpoint of being able to perform heat molding even at a low steam pressure and preventing a decrease in heat resistance of the obtained foamed molded product, it is preferable that the following formula (6) is satisfied, and the following formula (7) is satisfied. Is more preferable, the following formula (8) is more preferably satisfied, and the following formula (9) is particularly preferable. However, the units of Ti and Ts in the formula are both ° C.
(Equation 10)
3 (° C.) ≦ Ti−Ts ≦ 40 (° C.) (6)
(Equation 11)
5 (° C.) ≦ Ti−Ts ≦ 40 (° C.) (7)
(Equation 12)
7 (° C.) ≦ Ti−Ts ≦ 40 (° C.) (8)
(Equation 13)
9 (° C.) ≦ Ti−Ts ≦ 40 (° C.) (9)
表層部の補外融解開始温度（Ｔｓ）と、内層部の補外融解開始温度（Ｔｉ）との関係が前述した式（２）等を満足するように構成するためには、予め多層樹脂粒子の芯層と外層を形成するポリプロピレン系樹脂の融点を前述した示差走査熱量計によって測定し、前述した（１）式のように好ましい樹脂の組合せを選択することが好ましい。 In order to configure the relationship between the extrapolation melting start temperature (Ts) of the surface layer portion and the extrapolation melting start temperature (Ti) of the inner layer portion to satisfy the above-described equation (2) and the like, the multilayer resin particles must be prepared in advance. It is preferable that the melting point of the polypropylene resin forming the core layer and the outer layer is measured by the above-described differential scanning calorimeter, and a preferable resin combination is selected as in the above-mentioned formula (1).
本明細書におけるマイクロ示差熱分析（μＤＴＡ）は、ティ・エイ・インスツルメント・ジャパン社のマイクロ熱分析システム「２９９０型マイクロサーマルアナライザー」を使用し、２５℃から２５０℃まで昇温速度１０℃／秒の条件にて測定することとする。 The micro-differential thermal analysis (μDTA) in this specification uses a micro-thermal analysis system “2990 type micro-thermal analyzer” manufactured by TIA Instruments Japan, Inc., and the heating rate is 10 ° C. from 25 ° C. to 250 ° C. / Second.
図３及び図４は発泡粒子の表面に対するμＤＴＡ曲線の一例を示すものであり、これらの図を使用して発泡粒子の表層部の補外融解開始温度の求め方を説明する。図３は、多層発泡粒子の表層部と単層の発泡粒子の表層部のそれぞれに対するμＤＴＡ曲線の一例を示す。図３において、曲線Ｃｍが多層発泡粒子の表層部に対するμＤＴＡ曲線の一例であり、曲線Ｃｍ上のＰｍ点が融解開始温度であり、Ｐｍｅ点がベースライン（ＢＬ）と接線（ＴＬ）との交点である補外融解開始温度である。一方、曲線Ｃｎｍが単層の発泡粒子の表層部に対するμＤＴＡ曲線の一例であり、曲線Ｃｎｍ上のＰｎｍ点が融解開始温度であり、Ｐｎｍｅ点がベースライン（ＢＬ）と接線（ＴＬ）との交点である補外融解開始温度である。また図４は、多層発泡粒子（図３のものよりも多少表層部の補外融解開始温度が高いもの）の表面に対するμＤＴＡ曲線の一例を示す。図４において、曲線ＣｍがμＤＴＡ曲線であり、曲線Ｃｍ上のＰｍ点がその融解開始温度であり、Ｐｍｅ点がベースライン（ＢＬ）と接線（ＴＬ）との交点である補外融解開始温度である。 FIGS. 3 and 4 show an example of a μDTA curve with respect to the surface of the foamed particles, and a method of obtaining the extrapolation melting start temperature of the surface layer portion of the foamed particles will be described with reference to FIGS. FIG. 3 shows an example of a μDTA curve for each of the surface portion of the multilayer foamed particles and the surface portion of the single-layer foamed particles. In FIG. 3, a curve Cm is an example of a μDTA curve for the surface portion of the multilayer expanded particles, a point Pm on the curve Cm is a melting start temperature, and a point Pme is an intersection between the baseline (BL) and the tangent (TL). Is the extrapolation melting onset temperature. On the other hand, the curve Cnm is an example of the μDTA curve for the surface layer portion of the single-layer foamed particles, the Pnm point on the curve Cnm is the melting start temperature, and the Pnme point is the intersection of the baseline (BL) and the tangent (TL). Is the extrapolation melting onset temperature. FIG. 4 shows an example of a μDTA curve for the surface of the multilayer foamed particles (those having a slightly higher extrapolation melting start temperature at the surface layer portion than those in FIG. 3). In FIG. 4, a curve Cm is a μDTA curve, a point Pm on the curve Cm is its melting onset temperature, and a point Pme is an extrapolation melting onset temperature at the intersection of the baseline (BL) and the tangent (TL). is there.
尚、ここでいう融解開始温度とは、マイクロ示差熱分析によって得られるμＤＴＡ曲線におけるベースライン（ＢＬ）からμＤＴＡ曲線が下方に変化し始めた（時間当りの比熱が変化し始めた）温度を意味し、補外融解開始温度とは、上記μＤＴＡ曲線の前記ベースライン（ＢＬ）を高温側に延長した直線と、融解開始温度より高温側のμＤＴＡ曲線上における各点から引いた接線の内、該接線と上記ベースライン（ＢＬ）を高温側に延長した直線との間の角度が最大となる接線（ＴＬ）との交点の温度をいう。 Here, the melting onset temperature means a temperature at which the μDTA curve starts to change downward from the baseline (BL) in the μDTA curve obtained by micro differential thermal analysis (specific heat per hour starts to change). The extrapolated melting start temperature is defined as a straight line obtained by extending the baseline (BL) of the μDTA curve to a higher temperature side and a tangent line drawn from each point on the μDTA curve higher than the melting start temperature. The temperature at the intersection of the tangent line (TL) at which the angle between the tangent line and the straight line obtained by extending the base line (BL) to the high-temperature side is maximized.
上記マイクロ示差熱分析は、発泡粒子を装置のサンプルステージに固定し（１個の発泡粒子がそのままでは大きすぎる場合は例えば半分に切断する等して適当な大きさにして固定する）、次いで、発泡粒子の表面において無作為に選択した箇所に向けて、プローブチップ（発泡粒子の表層部に接触させる部分は縦横各０．２μｍの先端部を持つ）を下降させて発泡粒子の表層部に接触させた状態で実施される。 In the micro-differential thermal analysis, the foamed particles are fixed to a sample stage of an apparatus (if one foamed particle is too large as it is, it is fixed to an appropriate size, for example, cut in half, and then fixed). The probe tip (the part to be brought into contact with the surface layer of the foamed particles has a tip of 0.2 μm each in the vertical and horizontal directions) descends toward a randomly selected location on the surface of the foamed particles and contacts the surface layer of the foamed particles It is carried out in the state where it is made.
前記マイクロ示差熱分析による多層発泡粒子の表層部の補外融解開始温度は、異なる測定点１０点の測定結果より、最大値と最小値を除く８点の相加平均値が採用される。尚、最大値と最小値がそれぞれ複数ある場合はそれらを除く数点の相加平均値が採用される。また、平均１０点の測定値が全て同じ場合や、最大値と最小値の値しか得られなかった場合であって最大値と最小値の差が１０℃以内の場合には、１０点の相加平均値が採用される。尚、最大値と最小値の値しか得られなかった場合であって最大値と最小値の差が１０℃を超える場合には、更に異なる表面の１０点に対し測定して上記したと同じ要領で相加平均値を求め、それを採用すればよい。それでも条件に合わない場合には更に同じ操作を繰り返す。
以上のμＤＴＡによる結果は、多層発泡粒子の表層部の補外融解開始温度の低下が、成形時に必要な最低融着温度の低下に寄与していることを示している。
As the extrapolation melting start temperature of the surface layer portion of the multilayer expanded particles by the micro differential thermal analysis, eight arithmetic mean values excluding the maximum value and the minimum value from the measurement results at ten different measurement points are employed. When there are a plurality of maximum values and a plurality of minimum values, arithmetic mean values of several points other than those are adopted. If the measured values at the average of 10 points are all the same or only the maximum and minimum values are obtained and the difference between the maximum and minimum values is within 10 ° C, the 10 points The average value is adopted. If only the maximum value and the minimum value are obtained and the difference between the maximum value and the minimum value exceeds 10 ° C., the measurement is performed on 10 points on different surfaces and the same procedure as described above is performed. Then, the arithmetic mean value is obtained, and the obtained value may be used. If the condition is still not met, the same operation is repeated.
The above results of μDTA show that the decrease in the extrapolation melting start temperature of the surface layer portion of the multilayer expanded particles contributes to the decrease in the minimum fusion temperature required during molding.
また、多層発泡粒子の表層部の補外融解開始温度が低下するメカニズムは定かではないが多層樹脂粒子を発泡する際、芯層を構成する樹脂の融点を基準に発泡させる。多層樹脂粒子の外層は、外層を構成する樹脂の融点よりも高い温度から急冷されることとなるから低融点結晶のスメチカ構造が多くなり、多層発泡粒子の表層部の補外融解開始温度が低下すると考えられる。 メ カ ニ ズ ム Also, the mechanism by which the extrapolation melting start temperature of the surface layer portion of the multilayer foamed particles is lowered is not clear, but when the multilayer resin particles are foamed, they are foamed based on the melting point of the resin constituting the core layer. Since the outer layer of the multilayer resin particles is rapidly cooled from a temperature higher than the melting point of the resin constituting the outer layer, the smectic structure of the low melting point crystal increases, and the extrapolation melting start temperature of the surface layer portion of the multilayer expanded particles decreases. It is thought that.
発泡粒子の型内成形においては、発泡粒子相互の融着は発泡粒子表面同士で行なわれるため、発泡粒子の表面のみを熱分析する意義は大きい。発泡粒子の表面のみの融解開始の傾向をＤＳＣ法で知ることは不可能と思われる。それを可能にするのがμＤＴＡである。また、μＤＴＡで昇温速度を１秒あたり１０℃としているが、この速度は、実際の型内成形に際して発泡粒子を加熱する際の昇温速度に近いものである（このような速い昇温速度はＤＳＣ法では困難である）。従って、このような実際の型内成形に近似した昇温速度で分析する意義は大きい。このような理由から本発明では、多層発泡粒子の表層部に対するマイクロ示差熱分析（μＤＴＡ）を採用した。この測定に基づく補外融解開始温度は、厳密な意味での融解開始の温度を示していないかもしれないが、補外融解開始温度の温度の高低の傾向と成形温度の高低の傾向とはよく一致している。また、補外融解開始温度は誤差が少ないのでより再現性に優れる。 内 In the in-mold molding of the foamed particles, since the fusion of the foamed particles is performed between the surfaces of the foamed particles, it is significant to analyze only the surface of the foamed particles. It seems impossible to determine the tendency of only the surface of the expanded particles to start melting by the DSC method. ΜDTA makes it possible. Further, the heating rate in μDTA is set to 10 ° C. per second, but this heating rate is close to the heating rate when heating the expanded particles in actual in-mold molding (such a fast heating rate). Is difficult with the DSC method). Therefore, it is of great significance to analyze at a temperature rise rate similar to such actual in-mold forming. For this reason, the present invention employs micro-differential thermal analysis (μDTA) for the surface portion of the multilayer expanded particles. The extrapolated melting onset temperature based on this measurement may not indicate the melting onset temperature in a strict sense, but the tendency of the extrapolated melting onset temperature and the molding temperature is not well. Match. In addition, the extrapolation melting start temperature has less error, so that the reproducibility is more excellent.
以上のμＤＴＡによる結果は、発泡粒子における表層部の補外融解開始温度が内層部の補外融解開始温度より低くなる。このことから、成型時に必要な最低融着温度の低下に寄与していることを示している。 As a result of the above μDTA, the extrapolated melting start temperature of the surface layer portion of the expanded particles is lower than the extrapolated melting start temperature of the inner layer portion. This indicates that it contributes to the lowering of the minimum fusion temperature required during molding.
本発明の発泡粒子は、見かけ密度が１０ｇ／Ｌ〜５００ｇ／Ｌであることが好ましい。見かけ密度が１０ｇ／Ｌ未満の場合は、発泡粒子が連続気泡化となり発泡成形体を得ることができない虞がある。一方、見かけ密度が５００ｇ／Ｌを超える場合は、得られた発泡成形体の密度が大きすぎて、断熱性、緩衝性、軽量性等の発泡体特有の物性が失われる虞がある。 発 泡 The foamed particles of the present invention preferably have an apparent density of 10 g / L to 500 g / L. If the apparent density is less than 10 g / L, the foamed particles may become open cells and a foamed molded article may not be obtained. On the other hand, when the apparent density exceeds 500 g / L, the density of the obtained foamed molded article is too large, and there is a possibility that physical properties specific to the foam such as heat insulating property, cushioning property and light weight property may be lost.
上記発泡粒子の見かけ密度（ｇ／Ｌ）は、発泡粒子の重量（ｇ）をその見かけ体積（Ｌ）で除すことにより算出される。発泡粒子の見かけ体積（Ｌ）は、２３℃、大気圧下に４８時間以上放置された発泡粒子約５ｇを２３℃の水１００ｃｍ3が収容されたメスシリンダー内の水に水没させたときの排除体積を読み取り、これをリットル単位に換算することにより求まる。この測定には発泡粒子重量が０．５０００〜１０．００００ｇ、かつ発泡粒子の見かけ体積が５０〜９０ｃｍ3となる量の複数個の発泡粒子が使用される。 The apparent density (g / L) of the expanded particles is calculated by dividing the weight (g) of the expanded particles by the apparent volume (L). The apparent volume (L) of the foamed particles is about 5 g of the foamed particles left at 48 ° C. for more than 48 hours at 23 ° C., when the water is immersed in water in a measuring cylinder containing 100 cm 3 of water at 23 ° C. It is determined by reading the volume and converting it to liters. In this measurement, a plurality of foamed particles having an amount of foamed particles of 0.5000 to 10.0000 g and an apparent volume of the foamed particles of 50 to 90 cm 3 are used.
本発明の発泡粒子は、実質的に無架橋である。実質的に無架橋であるとは、特定条件下における沸騰キシレンに対する不溶分の割合が、試料の１重量％以下の場合をいう。 発 泡 The expanded particles of the present invention are substantially non-crosslinked. The term "substantially non-crosslinked" means that the proportion of the insoluble component in boiling xylene under specific conditions is 1% by weight or less of the sample.
即ち、多層樹脂粒子における芯層のポリプロピレン系樹脂、外層のポリプロピレン系樹脂、内層部及び表層部からなる発泡粒子、加熱成型により得られた発泡成形体を問わず、それぞれを試料とし（キシレン１００ｇ当たり試料１ｇ使用）、これを常圧において沸騰キシレン中に８時間浸漬後、ＪＩＳ Ｚ ８８０１（１９６６年）に定められている７４μｍの金網で速やかに濾過し、該金網上に残った沸騰キシレン不溶分の重量を測定し、この不溶分の割合が試料の１重量％以下の場合を実質的に無架橋という。 That is, regardless of the polypropylene resin of the core layer, the polypropylene resin of the outer layer, the foamed particles composed of the inner layer portion and the surface layer portion, and the foamed molded product obtained by heat molding in the multilayer resin particles, each was used as a sample (per 100 g of xylene). The sample was immersed in boiling xylene for 8 hours at normal pressure, then quickly filtered through a 74 μm wire mesh specified in JIS Z 8801 (1966), and the boiling xylene-insoluble matter remaining on the wire mesh was removed. Is measured, and the case where the proportion of the insoluble content is 1% by weight or less of the sample is called substantially non-crosslinked.
不溶分の含有率Ｐ（％）を式（１０）で表すと下式の通りである。
（数１４）
Ｐ（％）＝（Ｍ÷Ｌ）×１００・・・（１０）
ただし、Ｍは不溶分の重量（ｇ）、Ｌは試料の重量（ｇ）である
The content P (%) of the insoluble component is represented by the following formula when expressed by the formula (10).
(Equation 14)
P (%) = (M ÷ L) × 100 (10)
Here, M is the weight (g) of the insoluble matter, and L is the weight (g) of the sample.
本発明において発泡粒子の示差走査熱量測定によって得られるＤＳＣ曲線は、ポリプロピレン系樹脂に固有の吸熱曲線ピーク（以下、単に「固有ピーク」という）と、該吸熱曲線ピークよりも高温側の吸熱曲線ピーク（以下、単に「高温ピーク」という）とを少なくとも示し、且つ該高温側の吸熱曲線ピークの熱量が全ての吸熱曲線ピークの熱量の合計に対して１５％〜７０％であることが好ましい。かかる発泡粒子は、独立気泡率が高く、加熱成型に好適な発泡粒子である。 In the present invention, the DSC curve obtained by differential scanning calorimetry of the expanded particles includes an endothermic curve peak unique to the polypropylene resin (hereinafter, simply referred to as “inherent peak”) and an endothermic curve peak higher than the endothermic curve peak. (Hereinafter simply referred to as “high-temperature peak”), and the calorific value of the endothermic curve peak on the high-temperature side is preferably 15% to 70% with respect to the total calorific value of all the endothermic curve peaks. Such expanded particles have a high closed cell ratio and are suitable for heat molding.
前記した高温ピークの熱量が全ての吸熱曲線ピークの熱量の合計に対して１５％未満の場合は、成型する際のスチーム圧力を低くできるものの、得られる発泡成形体の圧縮強度、エネルギー吸収量などが低下する虞がある。また７０％を超える場合は、発泡粒子を成形するに先立ち発泡粒子内に付与しなければならない空気圧が高くなりすぎたり、成形サイクルが長くなる虞れがある。 When the calorific value of the above-mentioned high-temperature peak is less than 15% of the total caloric value of all the endothermic curve peaks, the steam pressure at the time of molding can be lowered, but the compressive strength, energy absorption amount, etc. of the obtained foam molded article May decrease. On the other hand, if it exceeds 70%, there is a possibility that the air pressure which must be applied to the foamed particles prior to molding the foamed particles becomes too high or the molding cycle becomes longer.
かかる観点より、内層部を形成するポリプロピレン系樹脂がプロピレン−エチン共重合体である場合は、高温ピークの熱量が全ての吸熱曲線ピークの熱量の合計に対して２０％以上が好ましく、２５％以上がより好ましく、３０％以上がさらに好ましい。又、その上限値は、上記観点から６０％以下であることが好ましく、５０％以下がより好ましい。 From such a viewpoint, when the polypropylene resin forming the inner layer portion is a propylene-ethyne copolymer, the calorific value of the high-temperature peak is preferably 20% or more, more preferably 25% or more, based on the total calorific value of all endothermic curve peaks. Is more preferable, and 30% or more is further preferable. In addition, the upper limit is preferably 60% or less, more preferably 50% or less from the above viewpoint.
また、かかる観点より、内層部を形成するポリプロピレン系樹脂がプロピレン単独重合体である場合は、高温ピークの熱量が全ての吸熱曲線ピークの熱量の合計に対して２０％以上が好ましく、２５％以上がより好ましく、３０％以上がさらに好ましい。又、その上限値は６０％以下であることが好ましく、５０％以下であることがより好ましい。 From this viewpoint, when the polypropylene resin forming the inner layer portion is a propylene homopolymer, the calorific value of the high-temperature peak is preferably 20% or more, more preferably 25% or more, based on the total calorific value of all the endothermic curve peaks. Is more preferable, and 30% or more is further preferable. The upper limit is preferably 60% or less, more preferably 50% or less.
本発明における発泡粒子の全ての吸熱曲線ピークの熱量の合計（全熱量）は、６０Ｊ／ｇ〜１５０Ｊ／ｇであることが好ましい。該熱量が６０Ｊ／ｇ未満の場合は、圧縮などの物性が低下する虞がある。一方、１５０Ｊ／ｇを超える場合は、成形する際の二次発泡性が悪く隙間の多い発泡成形体となる虞がある。 合計 The total calorific value (total calorific value) of all the endothermic curve peaks of the expanded particles in the present invention is preferably from 60 J / g to 150 J / g. If the amount of heat is less than 60 J / g, physical properties such as compression may be reduced. On the other hand, when it exceeds 150 J / g, there is a possibility that a secondary molded article having poor secondary foamability at the time of molding and having many gaps may be formed.
更に、内層部を形成するポリプロピレン系樹脂がプロピレン−エチレン共重合体である場合は、吸熱曲線ピークの全熱量は、６０Ｊ／ｇ〜１００Ｊ／ｇであることが好ましい。
また、内層部を形成するポリプロピレン系樹脂がプロピレン単独重合体である場合は、吸熱曲線ピークの全熱量は、６０Ｊ／ｇ〜１５０Ｊ／ｇであることが好ましい。
Furthermore, when the polypropylene resin forming the inner layer portion is a propylene-ethylene copolymer, the total heat quantity at the endothermic curve peak is preferably from 60 J / g to 100 J / g.
When the polypropylene resin forming the inner layer portion is a propylene homopolymer, the total heat quantity at the endothermic curve peak is preferably from 60 J / g to 150 J / g.
吸熱曲線ピークの全熱量と、高温ピークの熱量の測定は、ＪＩＳ Ｋ７１２２（１９８７年）に準拠する測定方法により次のように行なう。
まず、発泡粒子２〜１０ｍｇを採取し、示差走査熱量計によって室温（１０〜４０℃）から２２０℃まで１０℃／分で昇温測定を行なう。かかる測定により得られたＤＳＣ曲線の一例を図１に示す。
The measurement of the total heat quantity of the endothermic curve peak and the heat quantity of the high temperature peak is performed as follows by a measuring method based on JIS K7122 (1987).
First, 2 to 10 mg of the foamed particles are collected, and the temperature is measured by a differential scanning calorimeter from room temperature (10 to 40 ° C.) to 220 ° C. at a rate of 10 ° C./min. FIG. 1 shows an example of a DSC curve obtained by such measurement.
図１のＤＳＣ曲線には、発泡粒子を構成するポリプロピレン系樹脂に由来する固有ピークａと、高温ピークｂが示され、高温ピークｂの熱量はそのピーク面積に相当するものであり、具体的には次のようにして求めることができる。 The DSC curve of FIG. 1 shows an intrinsic peak a derived from the polypropylene resin constituting the expanded particles and a high-temperature peak b, and the calorific value of the high-temperature peak b corresponds to the peak area. Can be obtained as follows.
まず、ＤＳＣ曲線上の８０℃に相当する点αと、発泡粒子の融解終了温度Ｔに相当するＤＳＣ曲線上の点βとを結ぶ直線（α−β）を引く。尚、上記融解終了温度Ｔとは、高温ピークｂの高温側におけるＤＳＣ曲線と高温側ベースラインとの交点をいう。 {Circle around (1)} First, a straight line (α-β) connecting a point α on the DSC curve corresponding to 80 ° C. and a point β on the DSC curve corresponding to the melting end temperature T of the foamed particles is drawn. The melting end temperature T refers to the intersection of the DSC curve on the high temperature side of the high temperature peak b and the high temperature side baseline.
次に上記の固有ピークａと高温ピークｂとの間の谷部に当たるＤＳＣ曲線上の点γからグラフの縦軸と平行な直線を引き、前記直線（α−β）と交わる点をδとする。高温ピークｂの面積は、ＤＳＣ曲線の高温ピークｂ部分の曲線と、線分（δ−β）と、線分（γ−δ）とによって囲まれる部分（図１において斜線を付した部分）の面積であり、これが高温ピークの熱量に相当する。
また、本発明でいう全ての吸熱曲線ピークの熱量の合計は、図１の固有ピークａと高温ピークｂとのＤＳＣ曲線と直線（α−β）とによって囲まれる部分の面積であり、これが吸熱曲線ピークの全熱量に相当する。
Next, a straight line parallel to the vertical axis of the graph is drawn from a point γ on the DSC curve corresponding to a valley between the above-mentioned specific peak a and the high-temperature peak b, and a point intersecting the straight line (α-β) is defined as δ. . The area of the high-temperature peak b is defined by the curve of the high-temperature peak b portion of the DSC curve, the line segment (δ-β), and the portion surrounded by the line segment (γ-δ) (the hatched portion in FIG. 1). Area, which corresponds to the calorific value of the hot peak.
In addition, the total calorific value of all endothermic curve peaks referred to in the present invention is the area of the portion surrounded by the DSC curve of the specific peak a and the high-temperature peak b in FIG. 1 and the straight line (α-β). It corresponds to the total heat of the curve peak.
尚、高温ピークｂは、上記のようにして測定した第１回目のＤＳＣ曲線には認められるが、第２回目に昇温して得られたＤＳＣ曲線には認められない。第２回目のＤＳＣ曲線には、図２に示すように、発泡粒子を構成するポリプロピレン系樹脂に固有の吸熱曲線ピーク（固有ピークａ）のみが認められる。 The high temperature peak b is observed in the first DSC curve measured as described above, but is not observed in the second DSC curve obtained by raising the temperature. In the second DSC curve, as shown in FIG. 2, only an endothermic curve peak (unique peak a) unique to the polypropylene resin constituting the expanded particles is observed.
尚、発泡粒子の固有ピークと高温ピークを上記の通り示差走査熱量測定装置によって測定するに際しては、発泡粒子１個当たりの重量が２ｍｇ未満の場合は、総重量が２〜１０ｍｇとなる複数個の発泡粒子をそのまま測定に使用すればよく、また、発泡粒子１個当たりの重量が２〜１０ｍｇの場合には、発泡粒子１個をそのまま測定に使用すればよく、また、発泡粒子１個当たりの重量が１０ｍｇを超える場合には、１個の発泡粒子を、複数個に切断して得た重量が２〜１０ｍｇとなる切断試料１個を測定に使用すればよい。ただし、この切断試料は、１個の発泡粒子をカッター等を使用して切断されたものであるが、故意に発泡粒子の非発泡の部分が多く含まれるなど、発泡粒子全体における非発泡の部分と発泡の部分との割合が大きく変わるように試料を切り出して切断試料とすることは当然避けるべきである。切断試料の作製例としては発泡粒子１個当たりの重量が１８ｍｇの場合には、任意の方向に向けた発泡粒子を垂直方向の真中より水平に切断すれば２個のほぼ同じ形状の約９ｍｇの切断試料が得られ、各切断試料は、当初から有する発泡粒子の表層部と内層部との割合は変わらない。このようにして得られた２個の切断試料の内の１個を上記の通り固有ピークと高温ピークの測定に使用すればよい。 When the intrinsic peak and the high-temperature peak of the expanded particles are measured by the differential scanning calorimeter as described above, when the weight per one expanded particle is less than 2 mg, a plurality of particles having a total weight of 2 to 10 mg are used. The expanded particles may be used for measurement as they are, and when the weight per expanded particle is 2 to 10 mg, one expanded particle may be used for measurement as it is. When the weight exceeds 10 mg, one cut sample having a weight of 2 to 10 mg obtained by cutting one foamed particle into a plurality may be used for measurement. However, this cut sample is obtained by cutting one foamed particle using a cutter or the like. However, a non-foamed portion of the whole foamed particle, such as intentionally including a large number of non-foamed portions of the foamed particle, is used. Naturally, it should be avoided to cut out the sample so that the ratio between the foamed portion and the foamed portion greatly changes and use it as a cut sample. As an example of preparing a cut sample, in the case where the weight per foamed particle is 18 mg, if the foamed particles directed in an arbitrary direction are cut horizontally from the center in the vertical direction, two pieces of about 9 mg of approximately the same shape are cut. Cut samples are obtained, and in each cut sample, the ratio of the surface layer portion and the inner layer portion of the foamed particles originally contained does not change. One of the two cut samples thus obtained may be used for the measurement of the unique peak and the high-temperature peak as described above.
次に、本発明の発泡粒子における高温ピークの技術的な意味、及び高温ピークの熱量と本発明の構成との関系について説明する。 Next, the technical meaning of the high-temperature peak in the expanded beads of the present invention and the relationship between the heat quantity of the high-temperature peak and the configuration of the present invention will be described.
高温ピーク熱量は、前記の通り第１回目のＤＳＣ曲線に現れることから、ポリプロピレン系樹脂の結晶構造に起因するものであり、この高温ピーク熱量、即ち結晶構造は樹脂の融点と発泡温度の差に強く影響されることが経験的に分かっている。 Since the high-temperature peak calorific value appears in the first DSC curve as described above, it is attributable to the crystal structure of the polypropylene-based resin, and the high-temperature peak calorie, that is, the crystal structure is determined by the difference between the melting point of the resin and the foaming temperature. Experience has shown that it is strongly affected.
又、一般的に発泡粒子を型内に充填してスチームで加熱成型する際に、発泡粒子相互が型内で二次発泡して融着するために必要な最低の飽和スチーム圧力（以下、最低スチーム圧力）が存在することが分かっている。尚、最低スチーム圧力に相当する温度を、最低融着温度という。 In general, when the foamed particles are filled in a mold and then heat-molded with steam, the minimum saturated steam pressure required for the foamed particles to undergo secondary foaming and fusion in the mold (hereinafter, the minimum saturated steam pressure). Steam pressure). The temperature corresponding to the minimum steam pressure is called the minimum fusion temperature.
前記高温ピークの熱量は、上記最低融着温度と密接な関係にあり、最低融着温度を決定する因子として作用することが経験的に知られている。又、同一のポリプロピレン系樹脂を用いた場合、高温ピーク熱量値が小さくなると最低融着温度が低くなるといった傾向がある。また、この高温ピークの熱量の値は発泡粒子の製造段階における発泡温度の高低の影響を強く受け、同一のポリプロピレン系樹脂を用いた場合、発泡温度が高くなると高温ピークの熱量値が小さくなる傾向がある。 熱 It has been empirically known that the heat quantity of the high-temperature peak is closely related to the minimum fusion temperature and acts as a factor for determining the minimum fusion temperature. When the same polypropylene resin is used, the lower the high-temperature peak calorific value, the lower the minimum fusion temperature tends to be. Also, the value of the calorific value of the high-temperature peak is strongly influenced by the level of the foaming temperature in the production stage of the expanded particles, and when the same polypropylene resin is used, the calorific value of the high-temperature peak tends to decrease as the foaming temperature increases. There is.
ところが、高温ピークの熱量が小さい発泡粒子を用いて発泡成形体を加熱成型すると、最低融着温度は相対的に低くなる傾向があるものの、発泡成形体の圧縮強度（剛性）等の強度物性等が相対的に低下する傾向がある。一方、高温ピーク熱量が大きい発泡粒子を用いて発泡成形体を加熱成型すると、発泡成形体の圧縮強度等の強度物性等が相対的に高くなる傾向があるものの、最低融着温度が相対的に高くなり、前述のように発泡成形体を製造する際に高いスチーム圧力を必要とするという問題が発生する。 However, when a foamed article is heated and molded using foamed particles having a small amount of heat at a high temperature peak, the minimum fusion temperature tends to be relatively low, but the strength properties such as the compressive strength (rigidity) of the foamed article, etc. Tends to decrease relatively. On the other hand, when the foamed molded article is subjected to heat molding using foamed particles having a large high-temperature peak calorie, the strength properties such as the compressive strength of the foamed molded article tend to be relatively high, but the minimum fusion temperature is relatively low. As described above, a problem arises in that a high steam pressure is required when producing a foam molded article.
即ち、最も好ましい発泡粒子は、最低融着温度が低いにも拘わらず、発泡成形体の圧縮強度等の強度物性等が相対的に高いという相反する性質を同時に有するものである。本発明の発泡粒子はかかる矛盾する性質を同時に満足するものであって、強度物性等に優れるポリプロピレン系樹脂の最低融着温度が効果的に低下されたものである。従って、本発明の発泡粒子を用いて発泡成形体の加熱成型を行なえば、圧縮強度等の機械的物性において実用的強度を有する成形体を従来の成型装置を用いて製造することができる。 That is, the most preferable expanded particles have the opposite properties that the strength properties such as the compressive strength of the expanded molded article are relatively high despite the low minimum fusion temperature. The expanded particles of the present invention satisfy such contradictory properties at the same time, and the minimum fusion temperature of the polypropylene-based resin having excellent strength properties and the like is effectively reduced. Therefore, if a foamed molded article is subjected to heat molding using the foamed particles of the present invention, a molded article having practical strength in mechanical properties such as compressive strength can be manufactured using a conventional molding apparatus.
次に、本発明の発泡粒子の高温ピークの熱量を、前述した分散媒放出発泡方法において調整する方法について説明する。即ち、発泡粒子は、前述したように、密閉容器内で水に多層樹脂粒子を発泡剤と共に分散させて加熱し、発泡剤を多層樹脂粒子に含浸させてから、低圧下に放出する方法により得ることができる。 Next, a method for adjusting the calorific value of the high-temperature peak of the foamed particles of the present invention in the above-described dispersion medium discharge foaming method will be described. That is, as described above, the foamed particles are obtained by dispersing the multilayer resin particles in water in a closed container together with a foaming agent, heating the resin, impregnating the multilayer resin particles with the foaming agent, and releasing the foamed particles under low pressure. be able to.
かかる分散媒放出発泡方法により前記多層樹脂粒子を発泡させる場合、芯層を構成するポリプロピレン系樹脂の融点を基準として、加熱温度、加熱時間を設定すれば、高温ピークの熱量が大きくすることができ、得られた発泡粒子は圧縮強度等の強度物性等の優れたものとすることができる。 When the multilayer resin particles are foamed by the dispersion medium release foaming method, by setting the heating temperature and the heating time based on the melting point of the polypropylene resin constituting the core layer, the calorific value of the high-temperature peak can be increased. The obtained foamed particles can have excellent strength properties such as compressive strength.
分散媒放出発泡方法における高温ピークの具体的な調節方法としては、多層樹脂粒子を水性媒体に分散させて加熱する際に、芯層のポリプロピレン系樹脂の融解終了温度（ｔｉｅ）以上とならないように昇温し、該樹脂の融点（ｔｉ）より２０℃低い温度以上、融解終了温度（ｔｉｅ）未満の範囲内の任意の温度（Ｔａ）で止めてその温度（Ｔａ）で十分な時間、好ましくは１０〜６０分程度保持し、その後、融点（ｔｉ）より１５℃低い温度から融解終了温度（ｔｉｅ）＋１０℃の範囲の任意の温度（Ｔｂ）に加熱し、その温度で止め、当該温度でさらに十分な時間、好ましくは１０〜６０分程度、保持してから多層樹脂粒子を密閉容器内から低圧下に放出して発泡させることが好ましい。 As a specific method of adjusting the high-temperature peak in the dispersion medium release foaming method, when the multilayer resin particles are dispersed in an aqueous medium and heated, the melting temperature of the polypropylene resin of the core layer does not exceed the melting end temperature (tie). The temperature is raised and stopped at an arbitrary temperature (Ta) within a range of not less than a temperature lower than the melting point (ti) of the resin by 20 ° C. and less than the melting end temperature (tie), and a sufficient time at the temperature (Ta), preferably It is maintained for about 10 to 60 minutes, and then heated from a temperature 15 ° C. lower than the melting point (ti) to an arbitrary temperature (Tb) in the range of melting end temperature (tie) + 10 ° C., stopped at that temperature, and further heated at that temperature. After holding for a sufficient time, preferably about 10 to 60 minutes, it is preferable to release the multilayer resin particles from the inside of the closed container under low pressure to cause foaming.
分散媒放出発泡方法において、温度Ｔａ、Ｔｂ、及び保持時間を上記のように設定することが好ましいのは、発泡粒子の高温ピークの熱量の大小が、主として、発泡粒子を製造する際の樹脂粒子に対する上記温度Ｔａと該温度における保持時間および上記温度Ｔｂと該温度における保持時間、ならびに昇温速度に依存するからである。 In the dispersion medium release foaming method, it is preferable that the temperatures Ta, Tb, and the holding time are set as described above because the magnitude of the amount of heat at the high temperature peak of the foamed particles is mainly due to the resin particles used when producing the foamed particles. This is because it depends on the temperature Ta and the holding time at the temperature, the temperature Tb and the holding time at the temperature, and the heating rate.
一般的に、発泡粒子の上記高温ピークの熱量は、温度ＴａまたはＴｂが上記温度範囲内において低い程、保持時間が長い程、大きくなる傾向を示す。通常、昇温速度は０．５〜５℃／分が採用される。これらの点を考慮して予備実験を繰り返すことにより、所望の高温ピーク熱量を示す発泡粒子の製造条件を容易に知ることができる。 Generally, the calorific value of the expanded particles at the high temperature peak tends to increase as the temperature Ta or Tb falls within the temperature range and as the holding time increases. Usually, a heating rate of 0.5 to 5 ° C./min is employed. By repeating the preliminary experiment in consideration of these points, it is possible to easily know the production conditions of the expanded particles having the desired high-temperature peak calorific value.
尚、以上説明した発泡時の温度範囲は、発泡剤として無機系物理発泡剤を使用した場合の適切な温度範囲である。有機系物理発泡剤が併用された場合には、その種類や使用量に応じてその適切な温度範囲は上記温度範囲よりもそれぞれ低温側にシフトする傾向がある。 The temperature range during foaming described above is an appropriate temperature range when an inorganic physical foaming agent is used as a foaming agent. When an organic physical foaming agent is used in combination, the appropriate temperature range tends to shift to a lower temperature side than the above-mentioned temperature range depending on the type and amount used.
本発明の発泡粒子は、大気圧下で熟成した後、必要に応じて気泡内圧を高めてから、加熱成型することが発泡粒子相互の隙間がない発泡成形体を得ることができるので好ましく、又得られる発泡成形体の圧縮強度等の物性も向上するので好ましい。 The foamed particles of the present invention are preferably matured under atmospheric pressure, and then, if necessary, after increasing the internal pressure of the cells, heat-molded to obtain a foamed molded article having no gap between the foamed particles. It is preferable because the physical properties such as the compressive strength of the obtained foamed molded article are also improved.
尚、発泡粒子の気泡内圧を高める場合には、密閉容器に発泡粒子を入れ、該容器内に加圧空気を供給した状態で適当な時間放置して発泡粒子内に加圧空気を浸透させればよい。かかる方法で製造される発泡成形体の見かけ密度は目的によって任意に選定できるが、通常は９ｇ／Ｌ〜６００ｇ／Ｌの範囲である。なお、発泡成形体の見かけ密度は、試験片の外寸法（Ｌ）とその重量（ｇ）により求められる。 In order to increase the internal pressure of the foamed particles, the foamed particles are placed in a closed container, and the compressed air is allowed to permeate into the foamed particles by leaving the container under the supply of pressurized air for an appropriate time. Just fine. The apparent density of the foam molded article produced by such a method can be arbitrarily selected depending on the purpose, but is usually in the range of 9 g / L to 600 g / L. The apparent density of the foamed molded article is obtained from the outer dimensions (L) of the test piece and its weight (g).
又、上記気泡内圧が高められた発泡粒子は、水蒸気や熱風を用いて加熱することによって、より高発泡倍率の発泡粒子とすることが好ましい。かかる高発泡倍率の発泡粒子を用いて加熱成型を行なうと、高発泡倍率の発泡成形体を容易に得ることができる。 発 泡 In addition, it is preferable that the foamed particles having an increased internal bubble pressure be foamed particles having a higher expansion ratio by heating using steam or hot air. When heat molding is performed using the expanded particles having a high expansion ratio, a foam molded article having a high expansion ratio can be easily obtained.
発泡成形体は、前記発泡粒子を必要に応じて内圧を高めてから、加熱及び冷却が可能であってかつ開閉し密閉できる型内に充填し、飽和スチームを供給して型内で発泡粒子同士を加熱して膨張させて融着させ、次いで冷却して型内から取り出すバッチ式の型内加熱成形法を採用して製造することが好ましい。 The foamed molded article is prepared by increasing the internal pressure of the foamed particles as necessary, filling the mold in a mold that can be heated and cooled, and can be opened and closed and sealed, and supplies saturated steam to form the foamed particles in the mold. It is preferable to adopt a batch-type in-mold heat molding method in which the is heated to expand and fuse, then cooled and taken out of the mold.
該バッチ式の型内加熱成形法で使用される成形機としては、既に数多くの成形機が世界中に存在し、国によって多少異なるものの、その耐圧は、０．４１ＭＰａ(Ｇ)又は０．４５ＭＰａ(Ｇ)のものが多い。従って、発泡粒子同士を膨張させて融着させる際の飽和スチームの圧力は、０．４５ＭＰａ(Ｇ)以下であることが好ましく、０．４１ＭＰａ(Ｇ)以下であることがより好ましい。 As a molding machine used in the batch-type in-mold heating molding method, there are already a large number of molding machines in the world, and although they vary somewhat depending on the country, the pressure resistance is 0.41 MPa (G) or 0.45 MPa. Many of (G). Therefore, the pressure of the saturated steam when expanding and fusing the expanded particles is preferably 0.45 MPa (G) or less, more preferably 0.41 MPa (G) or less.
本発明の発泡粒子は、連続式成形法によって発泡成形体にすることもできる。
該連続式成形法においては、前記発泡粒子を必要に応じて気泡内圧を高めてから、通路内の上下に沿って連続的に移動するベルト間に連続的に供給し、飽和スチーム供給領域（加熱領域）を通過する際に発泡粒子同士を膨張融着させ、その後冷却領域を通過させて冷却し、次いで得られた成形体を通路内から取り出し、適宜の長さに順次切断することにより発泡成形体が得られる。そのような連続式成形法は、例えば特開平９−１０４０２６号、特開平９−１０４０２７号及び特開平１０−１８０８８８号等に記載されている。
The expanded particles of the present invention can be formed into an expanded molded article by a continuous molding method.
In the continuous molding method, the foamed particles are increased in internal pressure as necessary, and then continuously supplied between belts moving continuously up and down in a passage, so that a saturated steam supply region (heating Area), the expanded particles are expanded and fused together, then cooled by passing through a cooling area, and then the obtained molded body is taken out of the passage and cut into appropriate lengths in order to form the foam. The body is obtained. Such a continuous molding method is described in, for example, JP-A-9-104026, JP-A-9-104027 and JP-A-10-180888.
又、本発明の発泡粒子を用いて得られる発泡成形体は、ＡＳＴＭ−Ｄ２８５６−７０の手順Ｃに基づく連続気泡率が４０％以下であることが好ましく、３０％以下であることがより好ましく、２５％以下であることが特に好ましい。連続気泡率が小さい成形体ほど、機械的強度に優れるものとなる。 Further, the foamed molded article obtained by using the foamed particles of the present invention preferably has an open cell rate of 40% or less, more preferably 30% or less, based on Procedure C of ASTM-D2856-70, It is particularly preferred that it is 25% or less. A molded article having a smaller open cell ratio has better mechanical strength.
また、本発明の発泡粒子を用いて得られる発泡成形体にはその表面の少なくとも一部に、表面装飾材を積層一体化することができる。そのようなラミネート複合タイプの型内発泡成形体の製造方法は、米国特許第５９２８７７６号、米国特許第６０９６４１７号、米国特許第６０３３７７０号、米国特許第５４７４８４１号、ヨーロッパ特許４７７４７６号、ＷＯ９８／３４７７０号、ＷＯ９８／００２８７号、日本特許第３０９２２２７号等の各公報に詳細に記載されている。 に は In addition, a surface decorative material can be laminated and integrated on at least a part of the surface of a foam molded article obtained by using the foam particles of the present invention. The production method of such a laminated composite type in-mold foam molded article is disclosed in US Pat. No. 5,928,776, US Pat. No. 6,096,417, US Pat. , WO98 / 00287, Japanese Patent No. 3092227, and the like.
また、本発明によって得られる発泡成形体中には、インサート材の全部または一部が埋設されるようにして該インサート材を複合一体化することができる。そのようなインサート複合タイプの型内発泡成形体の製造方法は、米国特許第６０３３７７０号、米国特許第５４７４８４１号、特開昭５９−１２７７７１４号、日本特許第３０９２２２７号等の各公報に詳細に記載されている。 イ ン サ ー ト In addition, in the foam molded article obtained by the present invention, the insert material can be combined and integrated so that all or a part of the insert material is embedded. The method for producing such an insert composite type in-mold foam molded product is described in detail in U.S. Pat. No. 6,033,770, U.S. Pat. No. 5,474,841, JP-A-59-1277714, and Japanese Patent No. 3092227. Have been.
以下に本発明について実施例および比較例を挙げて詳細に説明する。 The present invention will be described in detail below with reference to examples and comparative examples.
実施例１〜８、比較例１〜３において使用するポリプロピレン系樹脂の種類、示差走査熱量測定による樹脂の融解熱量（Ｊ／ｇ）、メルトフローレイト（ＭＦＲ）を表１に示した。 Table 1 shows the types of polypropylene resin used in Examples 1 to 8 and Comparative Examples 1 to 3, the heat of fusion (J / g) of the resin by differential scanning calorimetry, and the melt flow rate (MFR).
実施例１〜８
表２に示すポリプロピレン系樹脂（表中では樹脂（ｙ））１００重量部とホウ酸亜鉛粉末（気泡調整剤）０．０５重量部を押出機に供給し、加熱溶融混練して芯層形成用の第一の混合溶融樹脂を形成した。同時に、表２に示すポリプロピレン系樹脂（表中では樹脂（ｘ））を他の押出機に供給し、加熱溶融混練して外層形成用の第二の混合溶融樹脂を形成した。
Examples 1 to 8
100 parts by weight of a polypropylene resin shown in Table 2 (resin (y) in the table) and 0.05 part by weight of zinc borate powder (cell regulator) are supplied to an extruder, and heated and melt-kneaded to form a core layer. To form a first mixed molten resin. At the same time, a polypropylene-based resin (resin (x) in the table) shown in Table 2 was supplied to another extruder, and was heated and melt-kneaded to form a second mixed molten resin for forming an outer layer.
次に、前記芯層形成用の第一の混合溶融樹脂と外層形成用の第二の混合溶融樹脂とを共押出ダイに供給し、該ダイ内において、第二の混合溶融樹脂が第一の混合溶融樹脂のストランド状の周囲を覆うように、第一の混合溶融樹脂に第二の混合溶融樹脂を積層した。尚、第一の混合溶融樹脂の吐出量（ｙＡ）と第二の混合溶融樹脂の吐出量（ｘＢ）の比（ｙＡ／ｘＢ）は、２０／１で設定した。 Next, the first mixed molten resin for forming the core layer and the second mixed molten resin for forming the outer layer are supplied to a co-extrusion die, and in the die, the second mixed molten resin is subjected to the first mixed molten resin. The second mixed molten resin was laminated on the first mixed molten resin so as to cover the strand-shaped periphery of the mixed molten resin. Incidentally, the discharge amount of the first mixed molten resin (y A) and the discharge amount of the second mixed molten resin (x B) ratio (y A / x B) was set at 20/1.
次に積層された混合溶融樹脂を、共押出ダイからストランド状に押出し、直径が約１ｍｍであり、長さが直径の略１．５となるように切断して、１粒子当りの平均重量が２ｍｇの多層樹脂粒子を得た。該多層樹脂粒子の外層の表面積は、多層樹脂粒子の表面全体の８６％であった。該多層樹脂粒子の外層の厚みを表２に示した。多層樹脂粒子の外層厚みの測定は、前述した測定法に従って行なった。 Next, the laminated mixed molten resin is extruded into a strand shape from a co-extrusion die, cut so as to have a diameter of about 1 mm and a length of about 1.5, and the average weight per particle is reduced. 2 mg of multilayer resin particles were obtained. The surface area of the outer layer of the multilayer resin particles was 86% of the entire surface of the multilayer resin particles. Table 2 shows the thickness of the outer layer of the multilayer resin particles. The measurement of the outer layer thickness of the multilayer resin particles was performed according to the above-described measurement method.
前記多層樹脂粒子を用いて下記により発泡粒子を製造した。
４００リットルのオートクレーブに、前記多層樹脂粒子１００重量部、水２２０重量部、ドデシルベンゼンスルホン酸ナトリウム（界面活性剤）０．０５重量部とカオリン（分散剤）０．３重量部、表２に示す炭酸ガス（発泡剤）を添加し、攪拌しながら表２に示す発泡温度よりも５℃低い温度まで昇温してからその温度で１５分間保持した。次いで、発泡温度まで昇温して同温度で１５分間保持した。次いで、オートクレーブの一端を開放してオートクレーブ内容物を大気圧下に放出して発泡粒子を得た。
Using the multilayer resin particles, expanded particles were produced as follows.
In a 400 liter autoclave, 100 parts by weight of the multilayer resin particles, 220 parts by weight of water, 0.05 parts by weight of sodium dodecylbenzenesulfonate (surfactant) and 0.3 parts by weight of kaolin (dispersant) are shown in Table 2. Carbon dioxide gas (foaming agent) was added, the temperature was raised to a temperature lower by 5 ° C. than the foaming temperature shown in Table 2 with stirring, and the temperature was maintained for 15 minutes. Next, the temperature was raised to the foaming temperature and maintained at the same temperature for 15 minutes. Next, one end of the autoclave was opened, and the contents of the autoclave were released under atmospheric pressure to obtain expanded particles.
尚、多層樹脂粒子をオートクレーブから放出する間、オートクレーブ内の圧力が放出直前のオートクレーブ内の圧力に保たれるように、オートクレーブ内に炭酸ガスを供給しながら放出を行った。 During the release of the multilayer resin particles from the autoclave, the release was performed while supplying carbon dioxide gas into the autoclave so that the pressure in the autoclave was maintained at the pressure in the autoclave immediately before the release.
得られた発泡粒子を水洗し遠心分離機にかけてから、２４時間大気圧下に放置して養生した後、発泡粒子の見かけ密度、高温ピーク熱量、全体の熱量に対して高温ピーク熱量の割合、平均気泡径、表層部の補外融解開始温度（Ｔｓ）、内層部の補外融解開始温度（Ｔｉ）、表層部の補外融解開始温度（Ｔｓ）と内層部の融解開始温度（Ｔｉ）との差（表３中では、「Ｔｉ−Ｔｓ」とした）等を測定した。その結果を表３に示した。 After the obtained foamed particles were washed with water and centrifuged, and allowed to cure under atmospheric pressure for 24 hours, the apparent density of the foamed particles, the high-temperature peak calorific value, the ratio of the high-temperature peak calorific value to the total caloric value, average The bubble diameter, extrapolated melting start temperature (Ts) of the surface layer portion, extrapolated melting start temperature (Ti) of the inner layer portion, and extrapolated melting start temperature (Ts) of the surface layer portion and melting start temperature (Ti) of the inner layer portion The difference (in Table 3, "Ti-Ts") was measured. Table 3 shows the results.
尚、発泡粒子群の見かけ密度（ｇ／Ｌ）、発泡粒子の高温ピーク熱量（Ｊ／ｇ）及び平均気泡径の測定方法は、前述した方法に従って行なった。 The methods of measuring the apparent density (g / L), the high-temperature peak calorie (J / g) of the foamed particles, and the average cell diameter of the foamed particles were performed according to the methods described above.
表層部の補外融解開始温度（Ｔｓ）と内層部の補外融解開始温度（Ｔｉ）の測定方法は、前述した方法で測定した。 測定 The extrapolation melting start temperature (Ts) of the surface layer portion and the extrapolation melting start temperature (Ti) of the inner layer portion were measured by the methods described above.
外層に着色剤を入れて着色した多層樹脂粒子を作製し、実施例１〜８と同様に発泡させて発泡粒子を顕微鏡で観察したところ、着色された外層に相当する部分（発泡粒子の表層部）は発泡していなかった。 Multilayer resin particles colored by adding a coloring agent to the outer layer were prepared, foamed in the same manner as in Examples 1 to 8, and the expanded particles were observed with a microscope. A portion corresponding to the colored outer layer (surface layer portion of the expanded particles) ) Was not foamed.
実施例１〜８で得られた発泡粒子を用いて下記により発泡成形体を成形した。耐圧容器内において加圧空気を用いて表４に示す加熱成型時の内圧に高めた後、０．５９ＭＰａ（Ｇ）の飽和スチーム圧力に耐えうる小スケールの成形機を用いて、２５０ｍｍ×２００ｍｍ×５０ｍｍの成形空間を持つ金型内に、金型を完全に閉鎖せずに僅かな隙間（約１ｍｍ）を開けた状態で充填し、次いでスチーム圧力で金型内の空気を排気した後に完全に型締めし、表４に示す圧力のスチーム圧力を金型内に供給することによって加熱成型した。 (4) Using the foamed particles obtained in Examples 1 to 8, foamed molded articles were formed as follows. After increasing the internal pressure during heat molding shown in Table 4 using pressurized air in a pressure vessel, using a small-scale molding machine capable of withstanding a saturated steam pressure of 0.59 MPa (G), 250 mm × 200 mm × A mold having a molding space of 50 mm is filled with a small gap (about 1 mm) opened without completely closing the mold, and then the air in the mold is completely exhausted by exhausting the air with steam pressure. The mold was clamped, and heat molding was performed by supplying a steam pressure of the pressure shown in Table 4 into the mold.
加熱成型後、金型内の成形体の面圧が０．０５９ＭＰａ（Ｇ）となるまで水冷した後、成形体を金型から取り出し、６０℃で２４時間養生した後、室温まで冷却して発泡成形体を得た。 After heat molding, after water cooling until the surface pressure of the molded body in the mold becomes 0.059 MPa (G), the molded body is taken out of the mold, cured at 60 ° C. for 24 hours, cooled to room temperature, and foamed. A molded article was obtained.
表４に本実施例における加熱成型時のスチーム圧力、融着率を示した。 Table 4 shows the steam pressure and the fusion rate during the heat molding in this example.
前記した融着率の具体的な測定は、まず、得られた発泡成形体を、カッターナイフで成形体の厚み方向に約１０ｍｍの切り込みを入れた後、手で切り込み部から発泡成形体を破断した。次に、破断面に存在する発泡粒子の個数（ｎ）と、材料破壊した発泡粒子の個数（ｂ）を測定し、（ｎ）と（ｂ）の比（ｂ／ｎ）×１００（％）の値を融着率とした。 The specific measurement of the above-mentioned fusion ratio is as follows. First, after cutting the obtained foamed molded body with a cutter knife into a cut of about 10 mm in the thickness direction of the molded body, break the foamed molded body from the cut portion by hand. did. Next, the number (n) of the foamed particles existing in the fracture surface and the number (b) of the foamed particles whose material was destroyed were measured, and the ratio (b / n) × 100 (%) of (n) and (b) was measured. Was defined as the fusion ratio.
表４に示す加熱成型時の発泡粒子の内圧の測定は次のように行なった。
内圧が高められた加熱成型直前の発泡粒子群を加圧タンク内から取り出してから６０秒以内に、発泡粒子は通過させないが空気は自由に通過できるサイズの針穴を多数穿設した７０ｍｍ×１００ｍｍ程度のポリエチレン製袋の中に収容して気温２３℃、相対湿度５０％の大気圧下の恒温室に移動する。続いてその恒温内の秤に載せて重量を読み取った。その重量の測定は、上記した発泡粒子群を加圧タンク内から取出してから１２０秒後とした。このときの重量をＱ（ｇ）とした。続いてその袋を同恒温室に４８時間放置した。発泡粒子内の加圧空気は時間の経過と共に気泡膜を透過して外部に抜け出すため発泡粒子群の重量はそれに伴って減少し、４８時間後では平衡に達しているため実質的にその重量は安定した。上記４８時間後に再度その袋の重量を測定し、このときの重量をＵ（ｇ）とした。続いて直ちに同恒温室内にて袋から発泡粒子群の全てを取り出して袋のみの重量を読み取った。その重量をＺ（ｇ）とした。上記のいずれの重量も０．０００１ｇまで読み取った。Ｑ（ｇ）とＵ（ｇ）の差を増加空気量Ｗ（ｇ）とし、次式より発泡粒子の内圧Ｐ（ＭＰａ）が計算される。尚、この内圧Ｐはゲージ圧に相当する。
（数１５）
Ｐ＝（Ｗ÷Ｍ）×Ｒ×Ｔ÷Ｖ・・・（１１）
The measurement of the internal pressure of the foamed particles during the heat molding shown in Table 4 was performed as follows.
Within 60 seconds after removing the foamed particle group immediately before heat molding with increased internal pressure from the inside of the pressurized tank, a large number of needle holes of a size not allowing the passage of the foamed particles but allowing the air to freely pass are formed in a size of 70 mm × 100 mm. The container is housed in a polyethylene bag of about 25 ° C. and is moved to a constant temperature room under the atmospheric pressure of 23 ° C. and 50% relative humidity. Subsequently, the weight was read by placing it on a balance within the constant temperature. The measurement of the weight was made 120 seconds after the above-mentioned expanded particle group was taken out of the pressurized tank. The weight at this time was defined as Q (g). Subsequently, the bag was left in the constant temperature room for 48 hours. The pressurized air in the foamed particles permeates through the cell membrane with the passage of time and escapes to the outside, so the weight of the foamed particles decreases accordingly, and after 48 hours has reached equilibrium, the weight is substantially reduced. Stable. After 48 hours, the weight of the bag was measured again, and the weight at this time was defined as U (g). Then, immediately, all the foamed particle groups were taken out of the bag in the same constant temperature room, and the weight of only the bag was read. The weight was defined as Z (g). All of the above weights were read to 0.0001 g. The difference between Q (g) and U (g) is defined as an increased air amount W (g), and the internal pressure P (MPa) of the expanded particles is calculated from the following equation. The internal pressure P corresponds to a gauge pressure.
(Equation 15)
P = (W ÷ M) × R × T ÷ V (11)
ただし、上式中、Ｍは空気の分子量であり、ここでは２８．８（ｇ／モル）の定数を採用する。Ｒは気体定数であり、ここでは０．００８３（ＭＰａ・Ｌ／（Ｋ・ｍｏｌ））の定数を採用する。Ｔは絶対温度を意味し、２３℃の雰囲気が採用されているので、ここでは２９６（Ｋ）の定数である。Ｖは発泡粒子群の見かけ体積から発泡粒子群中に占める基材樹脂の体積を差し引いた体積（Ｌ）を意味する。 Where, M is the molecular weight of air, and a constant of 28.8 (g / mol) is adopted here. R is a gas constant, and here, a constant of 0.0083 (MPa · L / (K · mol)) is adopted. T means an absolute temperature, and since an atmosphere of 23 ° C. is adopted, it is a constant of 296 (K) here. V means the volume (L) obtained by subtracting the volume of the base resin occupied in the expanded particle group from the apparent volume of the expanded particle group.
実施例１〜８において得られた発泡成形体の圧縮強度、見かけ密度及び耐熱性を測定し、その結果を表４に示した。 圧 縮 Compressive strength, apparent density, and heat resistance of the foamed molded articles obtained in Examples 1 to 8 were measured, and the results are shown in Table 4.
表４より実施例１〜８において加熱成型条件のスチーム圧力は、０．４５ＭＰａ(Ｇ)以下であり、さらに融着率が５０％以上であった。さらに実施例３〜８において加熱成型条件のスチーム圧力は、０．４１ＭＰａ(Ｇ)以下であった。このため、従来の成形機で充分成形できる発泡粒子であった。 よ り From Table 4, in Examples 1 to 8, the steam pressure under the heat molding conditions was 0.45 MPa (G) or less, and the fusion rate was 50% or more. Further, in Examples 3 to 8, the steam pressure under the heat molding conditions was 0.41 MPa (G) or less. For this reason, it was a foamed particle which can be sufficiently molded by a conventional molding machine.
発泡成形体の圧縮強度の測定は次のように行った。
まず、得られた発泡成形体から縦５０ｍｍ、横５０ｍｍ、厚み２５ｍｍの試験片（全面の表皮がカットされたもの）を切出した。次に、該試験片について、ＪＩＳ Ｚ ０２３４−１９７６ Ａ法に従って試験片温度２３℃、荷重速度１０ｍｍ／分の条件で歪が５５％に至るまで圧縮試験を行い、得られた応力−歪線図より５０％歪時の応力を読みとり、これを圧縮強度とした。
The measurement of the compressive strength of the foam molded article was performed as follows.
First, a test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm (the skin of the entire surface was cut) was cut out from the obtained foam molded article. Next, the test piece was subjected to a compression test under the conditions of a test piece temperature of 23 ° C. and a load speed of 10 mm / min until the strain reached 55% in accordance with JIS Z 0234-1976 A method, and a stress-strain diagram obtained. From this, the stress at the time of 50% strain was read, and this was taken as the compressive strength.
発泡成形体の見かけ密度の測定は前述した方法に従って行なった。 見 The apparent density of the foamed molded article was measured according to the method described above.
実施例１〜８の発泡粒子を用いて得られた発泡成形体の耐熱性の評価を行なった。
得られた発泡成形体から試験片サイズ厚み１０ｍｍ×幅４０ｍｍ×長さ２００ｍｍを切り取り、支持台の半径Ｒが１．２５ｍｍの高さ１００ｍｍ、スパン間距離１５０ｍｍの三点曲げに用いられる冶具に前記試験片を載せて、直径５ｍｍ、長さ５０ｍｍの円柱状の棒５ｇの重りを試験片の中央部に載せ、１４０℃のオーブン中に２２時間放置した。
加熱する前の冶具の下面から試験片の長さ方向の中央部分までの高さをＨｂとした加熱後の高さをＨａとして変形率は下式（１２）で求め、その値によって評価を行なった。結果を表４に示した。
（数１６）
変形率（％）＝（Ｈｂ−Ｈａ）／Ｈｂ ×１００・・・（１２）
※ ・・・変形率が１０％以下である。
○ ・・・変形率が１０％を超え、３０％以下である。
× ・・・変形率が３０％を超える。
The heat resistance of the foamed molded products obtained using the foamed particles of Examples 1 to 8 was evaluated.
A test piece having a thickness of 10 mm, a width of 40 mm and a length of 200 mm was cut out from the obtained foamed body, and the jig used for three-point bending with a support base having a radius R of 1.25 mm, a height of 100 mm, and a span distance of 150 mm was used. The test piece was placed, a weight of 5 g of a cylindrical rod having a diameter of 5 mm and a length of 50 mm was placed on the center of the test piece, and left in an oven at 140 ° C. for 22 hours.
The height from the lower surface of the jig before heating to the center in the length direction of the test piece is Hb, the height after heating is Ha, and the deformation ratio is obtained by the following equation (12). Was. The results are shown in Table 4.
(Equation 16)
Deformation rate (%) = (Hb−Ha) / Hb × 100 (12)
* ... The deformation rate is 10% or less.
: Deformation rate exceeds 10% and 30% or less.
X: Deformation rate exceeds 30%.
実施例３と実施例４、実施例５と実施例６の結果より、同じ多層樹脂粒子であっても発泡温度が高くなると得られる発泡粒子における内層部の補外融解開始温度と表層部の補外融解開始温度との差が広くなる傾向があった。 From the results of Examples 3 and 4, and Examples 5 and 6, even if the same multilayer resin particles are used, when the foaming temperature is increased, the extracellular melting start temperature of the inner layer portion and the surface layer portion of the foamed particles obtained are increased. The difference from the external melting onset temperature tended to widen.
実施例３と実施例８とを比較すると、発泡粒子の見かけ密度がほぼ同じであるが、実施例８の発泡粒子は高温ピーク熱量が大きいにもかかわらず、内層部と芯層部との融点差が大きいため（表２、実施例３：２．１℃、実施例８：２１℃）、実施例３の発泡粒子よりも低いスチーム圧力で成形できた。 A comparison between Example 3 and Example 8 shows that the apparent density of the expanded particles is almost the same, but the expanded particles of Example 8 have a high melting point between the inner layer and the core layer, despite having a large high-temperature peak calorific value. Due to the large difference (Table 2, Example 3: 2.1 ° C., Example 8: 21 ° C.), molding could be performed at a lower steam pressure than the foamed particles of Example 3.
比較例１〜３
表５に示したポリプロピレン系樹脂（表中では樹脂（ｙ））とポリプロピレン系樹脂（表中では樹脂（ｘ））を使用し、表５に示した多層樹脂粒子の外層の厚みとし、第一の混合溶融樹脂の吐出量（ｙＡ）と第二の混合溶融樹脂の吐出量（ｘＢ）の比（ｙＡ／ｘＢ）は、３．５／１で設定した以外は、実施例１〜８と同様に多層樹脂粒子を得た。なお、該多層樹脂粒子の外層の表面積は、多層樹脂粒子の表面全体の８６％であった。
Comparative Examples 1-3
Using the polypropylene-based resin (resin (y) in the table) and the polypropylene-based resin (resin (x) in the table) shown in Table 5, the thickness of the outer layer of the multilayer resin particles shown in Table 5 was determined. Example 1 except that the ratio (y A / x B ) of the discharge amount (y A ) of the mixed molten resin and the discharge amount (x B ) of the second mixed molten resin was set at 3.5 / 1. To 8 to obtain multilayer resin particles. The surface area of the outer layer of the multilayer resin particles was 86% of the entire surface of the multilayer resin particles.
前記多層樹脂粒子を用いて表５に示した炭酸ガスの添加量、発泡温度以外は実施例と同様に発泡粒子を製造した。
得られた発泡粒子を、実施例１〜８と同様に、発泡粒子を水洗し遠心分離機にかけてから、２４時間大気圧下に放置して養生した後、発泡粒子の見かけ密度、高温ピーク熱量、全体の熱量に対する高温ピーク熱量の割合、平均気泡径、表層部の補外融解開始温度（Ｔｓ）、内層部の補外融解開始温度（Ｔｉ）、表層部の融解開始温度（Ｔｓ）と内層部の補外融解開始温度（Ｔｉ）との差（表６中では、「Ｔｉ−Ｔｓ」とした）等を測定した。その結果を表６に示した。
Using the multilayer resin particles, expanded particles were produced in the same manner as in Example except for the amount of carbon dioxide added and the expansion temperature shown in Table 5.
The obtained foamed particles were washed with water and centrifuged in the same manner as in Examples 1 to 8, and after curing for 24 hours under atmospheric pressure, the apparent density of the foamed particles, high-temperature peak calorific value, Ratio of high-temperature peak calorific value to total calorific value, average cell diameter, extrapolation melting start temperature (Ts) of surface layer, extrapolation melting start temperature (Ti) of inner layer, melting start temperature of surface layer (Ts) and inner layer And the difference from the extrapolated melting start temperature (Ti) (in Table 6, "Ti-Ts") were measured. Table 6 shows the results.
外層に着色剤を入れて着色した多層樹脂粒子を作製し、比較例と同様に発泡させて発泡粒子を顕微鏡で観察したところ、比較例１〜３は、着色された外層に相当する部分（発泡粒子の表層部）は発泡していた。 Multilayer resin particles colored by adding a coloring agent to the outer layer were prepared, foamed in the same manner as in the comparative example, and the expanded particles were observed with a microscope. Comparative Examples 1 to 3 showed that the portions corresponding to the colored outer layer (foamed The surface layer of the particles was foamed.
比較例１〜３で得られた発泡粒子を用い、表７に示す加熱成型時の内圧に高めたこと、表７に示すスチーム圧力で加熱成型したこと以外、実施例１〜８と同様に加熱成型を行なった。
その結果、比較例１は、融着率が８０％であって、成形機の耐えうる飽和スチーム圧力が従来成型機の耐圧である０．４５ＭＰａ（Ｇ）を超える０．５０ＭＰａ（Ｇ）であった。
また、比較例２は、比較例１の発泡粒子を用いて飽和スチーム圧力を０．４３ＭＰａ（Ｇ）とした場合、成型後、金型を開けた際に発泡粒子相互が融着しておらず発泡成形体は得られなかった。
比較例３は、高温ピーク熱量が２６Ｊ／ｇと低いことからスチーム圧力は０．４３ＭＰａ（Ｇ）と従来成型機の耐圧である０．４５ＭＰａ（Ｇ）以下であったが発泡成形体の見かけ密度が同じである比較例１の圧縮強度と比較すると比較例３の圧縮強度は、約２２％も圧縮強度が低下するものであった。
なお、表７中における比較例３の融着率の※印は、得られた発泡成形体は、発泡粒子相互の融着はしているものの、発泡成形体を、カッターナイフで発泡成形体の厚み方向に約１０ｍｍの切り込みを入れた後、手で切り込み部から発泡成形体を破断し、破断面を電子顕微鏡で観察したところ、芯層部と表層部との界面で剥離していることが分かった。
Using the foamed particles obtained in Comparative Examples 1 to 3, heating was performed in the same manner as in Examples 1 to 8, except that the internal pressure during heat molding was increased as shown in Table 7 and heat molding was performed at the steam pressure shown in Table 7. Molding was performed.
As a result, in Comparative Example 1, the fusion rate was 80%, and the saturated steam pressure that the molding machine could withstand was 0.50 MPa (G), which exceeds the pressure resistance of the conventional molding machine, that is, 0.45 MPa (G). Was.
In Comparative Example 2, when the saturated steam pressure was set to 0.43 MPa (G) using the expanded particles of Comparative Example 1, the expanded particles did not fuse with each other when the mold was opened after molding. No foam molded article was obtained.
In Comparative Example 3, the steam pressure was 0.43 MPa (G) because the high-temperature peak calorific value was as low as 26 J / g, which was 0.45 MPa (G) or less, which is the pressure resistance of the conventional molding machine. , The compressive strength of Comparative Example 3 was about 22% lower than the compressive strength of Comparative Example 1 in which
In Table 7, the * mark of the fusion rate of Comparative Example 3 indicates that the obtained foamed molded product was fused with the foamed particles, but the foamed molded product was cut with a cutter knife. After making a cut of about 10 mm in the thickness direction, the foamed molded body was broken from the cut by hand, and when the fractured surface was observed with an electron microscope, it was found that it was peeled off at the interface between the core layer and the surface layer. Do you get it.
実施例９
表８に示すポリプロピレン系樹脂（表中では樹脂（ｙ））とポリプロピレン系樹脂（表中では樹脂（ｘ））を用いて外層にポリプロピレン系樹脂（ｘ）を用いて、断面が円筒状となる共押出ダイからストランド状に押出し、直径が約１．０ｍｍであり、直径と長さの比が略２．０になるように切断して、１粒子当りの平均重量が２ｍｇの円筒状の多層樹脂粒子を得た。得られた円筒状の多層樹脂粒子の表面は表層部で積層されていた。該多層樹脂粒子の外層の表面積は、多層樹脂粒子の表面全体の８９％であった。
Example 9
Using a polypropylene-based resin (resin (y) in the table) and a polypropylene-based resin (resin (x) in the table) shown in Table 8, the outer layer is made of a polypropylene-based resin (x), and the cross section is cylindrical. Extruded in a strand form from a co-extrusion die, cut to a diameter of about 1.0 mm, and a diameter to length ratio of about 2.0, and cut into a cylindrical multilayer having an average weight per particle of 2 mg. Resin particles were obtained. The surface of the obtained cylindrical multilayer resin particles was laminated on the surface layer. The surface area of the outer layer of the multilayer resin particles was 89% of the entire surface of the multilayer resin particles.
比較例４
表９に示すポリプロピレン系樹脂を用いて、断面が円筒状となる押出ダイからストランド状に押出し、直径が約１．０ｍｍであり、直径と長さの比が略２．０になるように切断して、１粒子当りの平均重量が２ｍｇの円筒状の多層樹脂粒子を得た。
Comparative Example 4
Using a polypropylene resin shown in Table 9, extruded into a strand shape from an extrusion die having a cylindrical cross section, and cut so as to have a diameter of about 1.0 mm and a diameter-to-length ratio of about 2.0. Thus, cylindrical multilayer resin particles having an average weight per particle of 2 mg were obtained.
実施例９、比較例４
前記円筒状の多層脂粒子を用いて以下のように円筒状の発泡粒子を製造した。
４００リットルのオートクレーブに、上記円筒状多層樹脂粒子５０重量部、水２２０重量部、ドデシルベンゼンスルホン酸ナトリウム（界面活性剤）０．０５重量部とカオリン（分散剤）０．３重量部、表８に示す炭酸ガス（発泡剤）を添加し、攪拌しながら表８及び表９に示す発泡温度よりも５℃低い温度まで昇温してからその温度で１５分間保持した。次いで、発泡温度まで昇温して同温度で１５分間保持した。次いで、オートクレーブの一端を開放してオートクレーブ内容物を大気圧下に放出して円筒状の発泡粒子を得た。それ以外は実施例１〜８と同様に行なった。
Example 9 and Comparative Example 4
Using the cylindrical multilayered fat particles, cylindrical foamed particles were produced as follows.
In a 400 liter autoclave, 50 parts by weight of the cylindrical multilayer resin particles, 220 parts by weight of water, 0.05 parts by weight of sodium dodecylbenzenesulfonate (surfactant) and 0.3 parts by weight of kaolin (dispersant), Table 8 Was added, and the temperature was raised to a temperature lower by 5 ° C. than the foaming temperature shown in Tables 8 and 9 while stirring, and then kept at that temperature for 15 minutes. Next, the temperature was raised to the foaming temperature and maintained at the same temperature for 15 minutes. Next, one end of the autoclave was opened, and the contents of the autoclave were discharged under atmospheric pressure to obtain cylindrical expanded particles. Other than that, it carried out similarly to Examples 1-8.
得られた円筒状の発泡粒子を水洗し遠心分離機にかけてから、２４時間大気圧下に放置して養生した後、該円筒状の発泡粒子の見掛け密度、高温ピーク熱量、全体の熱量に対する高温ピーク熱量の割合、平均気泡径、表層部の補外融解開始温度（Ｔｓ）、内層部の補外融解開始温度（Ｔｉ）、表層部の補外融解開始温度（Ｔｓ）と内層部の補外融解開始温度（Ｔｉ）との差（表１０中では、「Ｔｉ−Ｔｓ」とした）等を測定した。その結果を表１０及び表１１に示した。 After washing the obtained cylindrical foamed particles with water and centrifuging them, and leaving them to stand at atmospheric pressure for 24 hours to cure, the apparent density of the cylindrical foamed particles, the high-temperature peak calorie, the high-temperature peak with respect to the total calorie Ratio of calorific value, average bubble diameter, extrapolation melting start temperature (Ts) of the surface layer, extrapolation melting start temperature (Ti) of the inner layer, extrapolation melting start temperature (Ts) of the surface layer and extrapolation melting of the inner layer The difference from the starting temperature (Ti) (in Table 10, "Ti-Ts") and the like were measured. The results are shown in Tables 10 and 11.
次に、実施例９、比較例４で得られた円筒状の発泡粒子を用いて発泡成形体を製造した。 Next, a foam molded article was manufactured using the cylindrical foam particles obtained in Example 9 and Comparative Example 4.
気泡内圧を表１２に示す値に高め、金型を完全に閉鎖せずに僅かな隙間（約１ｍｍ）を開けた状態で充填し、次いでスチームで金型内の空気を排気した後に完全に型締めし、表１２に示す圧力のスチームを金型内に供給することによって加熱した以外は実施例１〜８と同様に加熱成型を行なった。得られた発泡成形体の圧縮強度、見かけ密度、空隙率を測定した結果を表１２に示した。 The internal pressure of the bubble was increased to the value shown in Table 12, the mold was not completely closed, and was filled with a small gap (about 1 mm) opened. Then, after the air in the mold was exhausted with steam, the mold was completely removed. Heating was carried out in the same manner as in Examples 1 to 8, except that heating was performed by supplying steam having the pressure shown in Table 12 into the mold. Table 12 shows the results obtained by measuring the compressive strength, apparent density, and porosity of the obtained foamed molded article.
空隙率の測定は次のように行った。
発泡成形体の空隙率（％）は、発泡成形体サンプルの外形寸法（２５ｍｍ×２５ｍｍ×１００ｍｍ）より求めた体積をａ（ｃｍ3）、該サンプルをアルコールを入れた目盛り付き容器のアルコール中に沈めた時の、目盛りの上昇分から求められるサンプルの真の体積をｂ（ｃｍ3 ）とし、下記式より求めた。
（数１７）
空隙率（％）＝｛１−（ｂ／ａ）｝×１００・・・（１３）
The measurement of the porosity was performed as follows.
The porosity (%) of the foamed molded article is a volume (cm 3 ) obtained from the external dimensions (25 mm × 25 mm × 100 mm) of the foamed molded article sample. The true volume of the sample obtained from the amount of increase in the scale at the time of submersion was defined as b (cm 3 ), and was obtained from the following equation.
(Equation 17)
Porosity (%) = {1- (b / a)} × 100 (13)
表１２より実施例９と比較例４とを比較すると、実施例９においては、スチーム圧力が低く、発泡粒子相互の融着も良好であった。比較例４についてはスチーム圧力が０．５５ＭＰａ（Ｇ）となり従来の成形機の０．４５ＭＰａ（Ｇ）を超えるものであった。又、実施例９で得られた発泡成形体は比較例４で得られた発泡成形体と比較すると空隙率が高いものであった。 よ り Comparing Example 9 with Comparative Example 4 from Table 12, in Example 9, the steam pressure was low and the fusion between the foamed particles was good. In Comparative Example 4, the steam pressure was 0.55 MPa (G), which exceeded 0.45 MPa (G) of the conventional molding machine. In addition, the foam molded article obtained in Example 9 had a higher porosity than the foam molded article obtained in Comparative Example 4.
比較例５
表１３に示したポリプロピレン系樹脂（表中では樹脂（ｙ））とポリエチレン系樹脂（表中では樹脂（ｘ））を使用した以外は、実施例１〜８と同様に行なったが積層された混合溶融樹脂を、共押出ダイからストランド状に押出し、直径が約１ｍｍであり、長さが直径の略１．５となるように切断した際に、芯層のポリプロピレン系樹脂と外層のポリエチレン系樹脂との接着性が低いため、芯層のポリプロピレン系樹脂が抜けてしまい多層樹脂粒子は得られなかった。
Comparative Example 5
Except that the polypropylene-based resin (resin (y) in the table) and the polyethylene-based resin (resin (x) in the table) shown in Table 13 were used, the same procedure as in Examples 1 to 8 was carried out, but the layers were laminated. When the mixed molten resin is extruded into a strand from a co-extrusion die and cut so as to have a diameter of about 1 mm and a length of about 1.5, a polypropylene resin of a core layer and a polyethylene resin of an outer layer are cut. Since the adhesiveness to the resin was low, the polypropylene resin in the core layer was removed, and multilayer resin particles could not be obtained.
Claims (6)
（数１）
１．５（℃）≦ｔｉ−ｔｓ≦３０．０（℃）・・・（１）
（但し、式中のｔｉ、ｔｓの単位はともに℃である。） A core layer formed of a polypropylene resin and an outer layer formed of a polypropylene resin, and a relationship between a melting point (ts) of the polypropylene resin of the outer layer and a melting point (ti) of the polypropylene resin of the core layer; Satisfies the formula (1), wherein a foaming agent is impregnated into the multilayer resin particles having an outer layer thickness of 30 μm or less to foam the foaming agent-impregnated multilayer resin particles in a heat-softened state. A method for producing expanded resin particles.
(Equation 1)
1.5 (° C.) ≦ ti−ts ≦ 30.0 (° C.) (1)
(However, the units of ti and ts in the formula are both ° C.)
（数２）
３（℃）≦Ｔｉ−Ｔｓ≦４０（℃）・・・（２）
（但し、式中のＴｉ、Ｔｓの単位はともに℃である。） The polypropylene resin foam according to claim 3, wherein the relation between the extrapolation melting start temperature (Ts) of the surface layer portion and the extrapolation melting start temperature (Ti) of the inner layer portion satisfies the expression (2). particle.
(Equation 2)
3 (° C.) ≦ Ti−Ts ≦ 40 (° C.) (2)
(However, the units of Ti and Ts in the formula are both ° C.)
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